Compounds for preventing or treating a viral infection

ABSTRACT

The invention which is the subject of the present application relates to a compound of structure I: A-B-C for use in the prophylaxis and/or treatment of a viral infection, and in particular for preventing and/or inhibiting viral replication, in which A is a quinoline or a quinoline-type group, B is a single amino acid or a peptide or polypeptide having a given amino acid sequence, C is an O-phenoxy group and the symbol “-” indicates that the entities A, B and C are chemically bonded within the compound I. 
     According to a particular embodiment, said compound is a protease inhibitor, in particular a caspase inhibitor, and more particularly the inhibitor Q-VD-OPh (N-(2(quinolyl)valyl-aspartyl-(2,6-difluorophenoxy)methyl ketone), optionally in an O-methylated form. 
     The invention relates also to a novel antiviral composition, and to a novel combination (or kit) comprising (i) said compound of structure I and (ii) at least one other antiviral agent, in particular at least one transcriptase inhibitor and/or at least one viral protease inhibitor.

The invention falls within the field of viral infections and thedevelopment of novel medicaments for the prophylaxis and/or treatment ofviral infections, especially retroviral, in particular lentiviral,infections, for example human immunodeficiency virus (HIV) and simianimmunodeficiency virus (SIV) infections.

The invention relates to a compound of structure I: A-B-C, for use inthe prophylaxis and/or treatment of a viral infection, in particular forpreventing and/or inhibiting viral replication, in which A is aquinoline or quinoline-type group, B is a single amino acid or a peptideor polypeptide having a given amino acid sequence, C is an O-phenoxygroup and the symbol “-” indicates that the entities A, B and C arechemically bonded within the compound I.

The invention relates more particularly to the compound Q-VD-OPh(N-(2(quinolyl)valyl-aspartyl-(2,6-difluorophenoxy)methyl ketone), foruse in the prophylaxis and/or treatment of a viral infection, inparticular for preventing and/or inhibiting viral replication.

The invention relates also to the use of said compound of structure I,and especially of the compound Q-VD-OPh, in the preparation of apharmaceutical composition for the prophylaxis and/or treatment of aviral infection and, in particular, for preventing and/or inhibitingviral replication.

The present invention relates also to a novel antiviral composition andto a novel combination (or kit) of suitable compounds for use in theprophylaxis and/or treatment of a viral infection, which comprise,consist essentially or consist of:

-   -   (i) at least one compound of structure I according to the        invention and    -   (ii) at least one other antiviral agent, for example a viral        protease inhibitor or a transcriptase, especially reverse        transcriptase, inhibitor.

Finally, the present invention relates to a method for preventing ortreating a viral infection in an animal or human.

Viral replication is the process by which a virus (DNA or RNA) hijacksand uses the machinery of the cell it infects to multiply. By way ofexample, the main steps of the replication of retroviruses, and inparticular of HIV viruses, are as follows: (1) fixing of the virus tothe surface of a cell of an animal or human organism by recognitionbetween virus surface proteins and receptors at the surface of said cell(for example the CD4 receptor); (2) penetration of the virus into thecell cytoplasm by fusion of the virus envelope with the cell membrane;(3) decapsidation of the virus (the virus separates from the matrix andfrom the capsid, which releases the two copies of the viral genome); (4)reverse transcription of the viral RNAs in the form of a proviral DNA byvirtue of reverse transcriptase (viral enzyme); (5) migration of theproviral DNA into the nucleus and integration of that DNA into the DNAof the host cell under the effect of integrase (viral enzyme); (6)transcription of the DNA of the cell into genomic RNA (unsplicedmessenger RNA (mRNA)) under the effect of the RNA polymerase of thecell; (7) splicing of the mRNA, by excision of the introns, to leaveonly the exons (which code for the proteins Gag, Pol and Env); (8)translation, in the rough endoplasmic reticulum, of the mRNA in the formof polypeptides; (9) maturation of the polypeptides in the Golgiapparatus, allowing functional polypeptides to be obtained; (10)assembly of the viral particles at the surface of the membrane byaccumulation of the multimerized structural polyproteins (Gag, p55), theviral nonstructural proteins (reverse transcriptase, integrase,protease) and the viral RNAs; (11) release of the virions by budding atthe surface of the infected cell; and finally (12) maturation of theviruses.

Viruses have developed various strategies for escaping the immune systemand facilitating their dissemination during the infection. Inparticular, the HIV virus has the particular feature of causing thecomplete breakdown of the immune system by attacking a key cell of theimmune system, the auxiliary T lymphocyte (CD4+ T lymphocyte), whichexpresses at its surface the CD4 molecule, a specific HIV receptor. Themonocytes-macrophages, the dendritic cells, the Langerhans cells and thecerebral microglial cells are likewise targets of HIV. The gradualdisappearance of the lymphocytes leads to a lack of control of viralreplication by the immune system, to the destruction of the lymphoidorgans, where the immune response takes place, and to the onset ofacquired immunodeficiency syndrome (AIDS), with the occurrence of severeopportunistic infections.

The mechanisms responsible for the disappearance of the CD4+ Tlymphocytes during infection by HIV are complex, and they have beenelucidated only partially.

The HIV viral particle is composed of a nucleocapsid which contains thesingle-stranded RNA dimer of positive polarity associated with thenucleocapsid protein, lysine tRNAs and the viral enzymes (reversetranscriptase, protease and integrase). The nucleocapsid is enclosed ina coat of matrix proteins which is covered by a lipid membrane borrowedfrom the host cell during budding of the viral particle. The membrane isprovided with spikes composed of envelope glycoprotein oligomers. Thestep of conversion of the RNA into bicatenary DNA during the viral cycleunder the action of a viral enzyme, reverse transcriptase, is the maincharacteristic of the retroviruses.

The viral genes gag, pol and env are retained in all retroviruses. Allthe products derived therefrom are present in the viral particle. Theycome from the cleavage of precursor polyproteins. The genes gag and envcode for structural proteins, and the gene pol codes for numerousenzymatic proteins.

The Gag proteins are obtained from the cleavage of the polyproteinPr55gag by viral protease. The cleavage releases the matrix protein, thecapsid protein, the nucleocapsid protein, as well as a 6 kDa protein.Recent works suggest that these processes play an essential role in thegenesis of infectious viral particles (Sticht et al., 2005; Ternois etal., 2005). These recent works have made it possible to generate, forthe first time, an HIV assembly inhibitor.

The envelope precursor gp160 is cleaved into a surface glycoproteingp120 (gp130 for SIVmac) and a transmembrane protein gp41 derived fromthe C-terminal region of the precursor. During its maturation, theprecursor gp160 is glycosylated and then cleaved by a cell protease inthe Golgi apparatus and then exported to the plasmic membrane. The twoglycoproteins derived from the cleavage remain associated bynon-covalent bonds. They form heteromers of envelope glycoproteins,which combine in oligomers to form the spikes of the virion.

The gene pol codes for three enzyme proteins: protease, reversetranscriptase and integrase. They are derived from the cleavage of thepolyprotein Gag-Pol (Pr160 gag-pol) during the morphogenesis of thevirion. Dimerization in the cell of the polyprotein Gag-Pol reveals theprotease activity coded for by the 5′-region of pol. The mature form ofthe protease, released by autocatalytic cleavage, remains in the dimericform p11 /p11 and is then able to cleave other sites present on thepolyproteins Pr160gag-pol and Pr55gag.

Reverse transcriptase is derived from the cleavage of the polyproteinPr160gag-pol in two steps by the viral protease during the assembly ofthe viral particle.

Located in the C-terminal position of the Pol region of the polyproteinGag-Pol, integrase is released in the form of a 32 kDa protein under theaction of the viral protease. Its oligomerization is required both forits incorporation into the viral particle and to exert its activity ofintegrating linear double-stranded viral DNA into the cell genome.

All of these works emphasize the major role of protease(s) in thegenesis of an infectious viral particle. Accordingly, as well as usingretrotranscriptase inhibitors or nucleoside analogues, the HIV therapyknown as highly active anti-retroviral therapy or “HAART” today includesone or more HIV protease inhibitors. This therapy leads to inhibition ofviral replication, an increase in the number of CD4 T lymphocytes and anindisputable clinical improvement.

However, in so far as no current treatment enables patients to be curedof AIDS, and HIV virus isolates are or are becoming resistant toexisting treatments, it is necessary to find other antiviral moleculeswhich allow viral infections in general and infections by retrovirusessuch as HIV in particular to be combated more effectively.

Many viral infections coincide with disturbances in the mechanisms thatcontrol cell death (Barber, 2001). In particular, many works indicatethat there is a relationship between in vitro or in vivo infection byHIV and an increase in the susceptibility to apoptosis of the Tlymphocytes. Apoptosis (or programmed cell death or even cell suicide)is the process by which cells trigger their self-destruction in responseto a signal (pro-apoptotic signal). The environment, interactionsbetween cells, the absence of nourishment for the cell, infection by apathogenic agent, are a few examples of pro-apoptotic signals. Apoptosisis a morphologically and biochemically defined form of cell death whichis characterized in vivo by the absence of an inflammatory response, theactivation of caspases and the cleavage of numerous proteins,fragmentation of the DNA, condensation of chromatin, cell contractionand the disassembly of cell structures to form vesicles incorporatedinto the membrane (apoptotic bodies). In vivo, this process culminatesin the phagocytosis of apoptotic bodies by other cells.

Precocious apoptosis of a cell infected by a virus can constitute adefence mechanism of the host; it allows the number of viral particlesreleased to be limited by interrupting viral replication. The cellendonucleases produced during apoptosis can act on the viral DNA andinhibit the synthesis of viral, structural and regulatory proteins andthe formation of infectious viral particles, thus limiting thedissemination of virions in the host.

Accordingly, many viruses act on the regulation of the apoptoticintracellular signals, either in order to keep themselves alive or tokeep the infected cell viable or to prevent the cell from being attackedby the effector cells of the immune system, and thus increase theefficacy of viral replication and permit greater production of virions.The majority of viruses have one or more genes permitting the synthesisof proteins whose effect is to suppress, at different stages, apoptosisof the cells they infect (antiapoptotic proteins). By retarding orinhibiting the death of the host cell, viruses promote the survival ofthe cell they infect and therefore their own survival, to the extent ofpromoting the occurrence of cancers in some cases.

Other viruses, on the other hand, have also developed strategies forcausing the death of the cells they infect, leading to celldeficiencies, in particular immune deficiencies (such as thoseassociated with AIDS), neuronal deficiencies (such as those associatedwith rabies) and epithelial deficiencies (such as those associated withhaemorrhagic fevers). In the case of immune deficiencies alone, theviruses are then able to propagate. Some viruses are additionallycapable of inducing apoptosis at a late phase of the infection, whichallows the virions to propagate into the neighbouring cells whileescaping the inflammatory and immune response of the host (Everett &McFadden, 1999).

The apoptotic processes induced by viruses are at the origin of celldisturbances which influence the clinical evolution of viral infections.Infection by HIV is a very representative example. Infection by HIV-1 isaccompanied by abnormal induction of apoptosis in the adult Tlymphocytes, the thymocytes and the haematopoietic precursors. Moreover,in a large number of patients, excess apoptosis affects all thelymphocyte populations (CD4 T, CD8 T and B), and the degree of apoptosiscorrelates with the evolution of the disease (Gougeon et al., 1996). Inaddition, in some patients infected by HIV, lymphocyte apoptosis isabnormally elevated in the lymphatic ganglions (Amendola et al., 1996),which constitute the main replication sites of the virus. Mostsurprising is that, in patients infected by HIV, the majority of the Tcells that undergo apoptosis are not infected by the virus (“bystander”effect) (Finkel et al., 1995). These observations suggest that thedestruction of the lymphocytes by HIV is the result of the activation bythe virus of cytopathogenic mechanisms which are both direct andindirect.

The regulation of apoptosis by HIV is all the more complex because thevirus is capable of manipulating the apoptotic machinery to itsadvantage by acting as both an activator and a repressor of apoptosis.HIV has in fact also developed mechanisms of inhibiting apoptosis inorder to escape the host's immune system.

Various studies have shown that other lentiviruses, in particular felineimmunodeficiency virus (FIV) and some strains of simian immunodeficiencyvirus (SIV), are also capable of inducing apoptosis and causing animmune deficiency syndrome in their natural host. Accordingly, withinthe scope of a study of different models of chronic lentiviralinfections in primates, the inventors of the present invention havepreviously shown that the CD4+ T lymphocytes are abnormally sensitive toapoptosis in the rhesus macaque infected by the pathogenic strainSIVmac251 (Hurtrel et al., 2005).

On the other hand, in models of chronic lentiviral infections ofprimates in which the infection, whatever the lentiviral isolate inquestion, does not cause AIDS (chimpanzees experimentally infected byHIV, African green monkeys naturally infected by SIVagm), there is noabnormal programming of apoptosis of the CD4+ T lymphocytes in vitro.However, this absence of disease is not linked to the absence ofpathogenic potential of the virus, since these viruses are capable ofinducing AIDS in macaques (Hurtrel et al., 2005). Accordingly, thesemodels of lentiviral infections underline the importance of factorsproper to the host, which will determine either the occurrence ofapoptosis associated with the development of AIDS, or the absence ofpathology.

One of the major components of the machinery of apoptosis is a family ofcysteine proteases called caspases (from the English cysteinylaspartate-specific proteases or cysteine aspartate proteases). Caspaseshave been found in many organisms, ranging from C. elegans to humans. Todate, more than about twelve caspases have been identified. Theseintracellular enzymes have a key role in apoptosis, inflammation,activation and cell differentiation.

Like other proteases, caspases are expressed in the form of proenzymeswhich undergo proteolytic maturation. These precursors are expressedconstitutively in the cell cytoplasm. The procaspases (from 30 to 50 kD)contain three domains: an N-terminal prodomain, a large subunit (about20 kD) and a small subunit (about 10 kD). Activation involvesproteolytic cleavage between the domains, followed by the association ofthe large and the small subunit, each of which contributes to the aminoacids of the active site, to form a heterodimer. The active matureenzymes function in the form of a tetramer composed of two heterodimers.The N-terminal domain of the caspases, whose length (from 23 to 216amino acids) and sequence vary greatly, is involved in the regulation ofthose enzymes.

The function of the caspases is determined by their substratespecificity, the length of their prodomain and the sequence of theprodomain. The caspases can be divided into three groups: theinflammatory caspases (group I), the initiator (or regulatory) caspases(group II) and the effector (or executor) caspases (group III) (Lavriket al., 2005). The long prodomain (more than 100 amino acids) of theinitiator caspases and of the inflammatory caspases acts as an apoptoticor proinflammatory signal integrator. The inflammatory caspases includecaspase-1, -4, -5, -11, -12, -13 and -14. They are involved in theinflammatory processes and play a central role in the activation ofcertain cytokines. The initiator caspases include caspase-2, -8, -9 and-10. They are located upstream of the apoptotic signalling cascades andare activated by autoproteolytic mechanisms in response to proapoptoticsignals. They then cleave and activate the effector caspases, which arelocated downstream of the signalling cascades, permitting amplificationof the apoptotic signal. The effector caspases include caspase-3, -6 and-7. They are involved directly in the execution or occurrence ofapoptosis; once activated by the initiator caspases, they cleavenumerous cell proteins, thus leading to dismantling of the cell orinactivation of other proteins (Thornberry and Labzebnik, 1998). Theproteins inactivated by the action of these caspases (approximately from2000 to 3000 substrates) include proteins which protect the cells fromapoptosis (antiapoptotic proteins), such as proteins of the Bcl-2family.

The caspases, the catalytic domain of which includes a cysteine residue(C), cleave their protein substrate(s) at specific consensus sitescontaining an aspartic residue which are located in the carboxy-terminalpart of the substrate. They exhibit substrate recognition motifs andhighly conserved catalytic motifs (Cryns et al., 1998).

The preferences or substrate specificities of individual caspases havebeen used to develop peptides which effectively enter into competitionwith the binding of the caspases to their substrate. Such syntheticinhibitors are now available commercially. Some broad-spectrum caspaseinhibitors include a single amino acid or a generally di- totetra-peptide amino acid sequence, which is optionally O-methylated andwhich is conjugated to a carboxy-terminal group such as fluoromethylketone (fmk), chloromethyl ketone (cmk), an aldehyde group (CHO) or adifluorophenoxy group (OPh). Such inhibitors have been describedespecially in patent application WO 02/183341. These caspase inhibitorsare capable of penetrating the cells and binding irreversibly (with theexception of inhibitors having an aldehyde group, whose binding isreversible) to the active site of the caspases. They accordingly act asproteolytic decoys by blocking proteolytic caspase cleavage, which isrequired for activation of said caspases and the production of an activetruncated caspase. Inhibitors having a carboxy-terminal group fmk or OPhhave been formulated for in vivo and in vitro applications.

Two of the most widely used caspase peptide inhibitors are theinhibitors Boc-D-fmk (tert-butyloxycarbonyl-Asp(O-methyl)-fluoromethylketone; Enzyme Systems Products, CalBiochem or R&D Systems) andz-VAD-fmk (N-benzyloxycarbonyl-Val-Ala-Asp-fluoromethyl ketone; EnzymeSystems Products, CalBiochem or R&D Systems). The Boc(tert-butyloxycarbonyl) and z (N-benzyloxycarbonyl) groups serve toblock the amino acid sequences D (Asp) or VAD (Val-Ala-Asp), while thefluoromethyl ketone group in the carboxy-terminal position facilitatesmembrane permeability. It has been shown that inhibition of theactivation of caspases by such inhibitors prevents the appearance of themorphological modifications which are characteristic of apoptosis(Chinnaiyan et al., 1997).

A more recently developed caspase inhibitor, Q-VD-OPh(N-(2(quinolyl)valylaspartyl-(2,6-difluorophenoxy)methyl ketone; EnzymeSystems Products, CalBiochem or R&D Systems), has increased efficacy,stability and permeability as compared with inhibitors having acarboxy-terminal group of the fluoromethyl ketone (fmk) type, andreduced toxicity, even when used in a high concentration; this inhibitorhas been found to be non-toxic at doses of up to 1 g/kg live weight,when administered to mice by the intraperitoneal route (Vera et al.,2005).

The inhibitor Q-VD-OPh has been found to be functional in vitro, indifferent cell types, and in vivo, in animal models, in particular inthe mouse and the rat. Moreover, it has been shown that it inhibitsvarious caspases, in particular caspase-1, -3, -8, -9, -10 and -12, withIC50 values ranging from 25 to 400 nM. Furthermore, Q-VD-OPh, like theinhibitors ZVAD-fmk and Boc-D-fmk, inhibits apoptosis in adose-dependent manner (Caserta et al., 2003).

It has been proposed that the inhibition of caspases or theoverexpression of the antiapoptotic protein Bcl-2 might prevent viralinfections by inhibiting apoptosis, and also disrupt viral production(Levine, 1996; Olsen, 1996; Liang, 1998; Wurzer, 2003). However, studiesconducted in vitro using the caspase inhibitor z-VAD-fmk did not enableviral replication to be inhibited (Gandhi et al., 1998; Petit et al.,2002). On the contrary, administration of the caspase inhibitorz-VAD-fmk to T-leukaemia cells (CEM) or to peripheral blood mononuclearcells (PBMC) exposed to the HIV-1 virus had the effect of increasingviral replication (Chinnaiyan et al., 1997). Similar results have beenobserved in the case of CEM cells expressing the CrmA (cytokine responsemodifier A) protein of the vaccinia virus, a viral caspase inhibitorthat inhibits especially activation of caspase-1, -6 and -8 (Chinnaiyanet al., 1997). This suggests that the results observed in the case ofthe inhibitor z-VAD-fmk are not specific to that inhibitor but ratherthe result of the inhibition of proapoptotic proteases. Furthermore, theinhibitor z-VAD-fmk is capable of stimulating endogenous viralreplication in activated PBMCs derived from patients who areHIV-1-positive but are asymptomatic (Chinnaiyan et al., 1997). Thetotality of these results suggests that apoptosis might help the host tolimit propagation of the virus and that, consequently, strategies aimedat inhibiting cell death might have deleterious consequences for theinfected host and might, in particular, contribute towards increasingthe viral load of an HIV-positive individual. This would be in agreementwith the fact that many viruses produce proteins that inhibit cell deathin the host (for example the CrmA protein produced by the vacciniavirus).

In view of these earlier results, the present invention appearssurprising. The results presented in the present application in factshow that the compound Q-VD-OPh not only permits inhibition of theapoptotic phenotype (caspase inhibition, DNA condensation andfragmentation) of the HIV-infected cells, but also inhibition of theirdeath and especially inhibition of viral replication.

The invention accordingly relates to the compound Q-VD-OPh or aderivative thereof and, more generally, to a structure I as defined inthe present application, for use as a medicament, in particular as anantiviral agent and more particularly as an antiretroviral agent. Saidcompound is used in particular for the prophylaxis and/or treatment of aviral infection, in particular in an animal or human, and moreparticularly for inhibiting viral replication in an animal or humaninfected by a virus.

The invention relates also to the use of at least one compound ofstructure I, in particular to the use of the compound Q-VD-OPh, in thepreparation of a pharmaceutical composition for the prophylaxis and/ortreatment of a viral infection, in particular in an animal or human, andmore particularly for preventing and/or inhibiting viral replication inan animal or human infected by a virus.

Unless indicated otherwise, each embodiment indicated in thisapplication applies independently and/or in combination with the otherembodiments described.

Said compound I comprises or consists of at least one amino acid, thatis to say a single amino acid or a plurality of amino acids in the formof a peptide or polypeptide having a given amino acid sequence, thecarboxyl group of said single amino acid or the C-terminal portion ofsaid peptide or polypeptide being bonded to an O-phenoxy group and theamine group of said single amino acid or the N-terminal end of saidpeptide or polypeptide being bonded to a quinoline or quinoline-typegroup. It has been shown that the use of carboxy-terminal O-phenoxygroups enables the efficacy of caspase inhibitors to be improved andtheir toxicity to be reduced (Caserta et al., 2003).

In other words, the compound of structure I is of the type A-B-C, Abeing a quinoline or quinoline-type group, B being a single amino acidor a peptide or polypeptide having a given amino acid sequence, and Cbeing an O-phenoxy group, the symbol “-” indicating that the entities A,B and C are chemically bonded within the compound I. According to aparticular embodiment, the groups A, B and C are bonded (or fused)covalently, for example by way of peptide bonds.

The term “quinoline” as used in the present application includes thestructure of the 1-aza-naphthalene type.

The expression “quinoline-type” as used in the present applicationincludes structures having a carbonyl group fixed in the 2- or3-position to the quinoline, in particular to the 1-aza-naphthalenestructure, for example quininic acid. This expression also includes themelatonin structure and similar structures. According to a particularembodiment, said quinoline-type group is the group 2-quinolylcarbonyl.

In a particular embodiment, the quinoline group is replaced by theindole structure. The expression “quinoline-type” then includesstructures having a carbonyl group fixed in the 2- or 3-position to theindole structure.

In a particular embodiment, the structure I is:

in which

-   -   B is a single amino acid or a peptide or polypeptide having a        given amino acid sequence,    -   R1 and R2 are selected from a hydrogen, an alkyl, an alkoxy, a        fluoro, a chloro, a carboxy, a carbonyl, an arylcarbonyl and an        amino, and    -   R3 and R4 are selected from a hydrogen, an alkyl, an alkoxy, a        fluoro, a chloro, a carboxy, a carbonyl, an arylcarbonyl and an        amino.

As used in the present application, the term “alkyl” refers to alkylgroups having preferably from approximately 1 to 20 carbon atoms, morepreferably from approximately 1 to 10 carbon atoms, for example 1, 2, 3,4, 5, 6, 7, 8, 9 or 10 carbon atoms. The term includes all theconfigurations of the alkyl groups. According to a particularembodiment, said alkyl group is a methyl group or an ethyl group.

As used in the present application, the term “alkoxy” or “alkoxyl”denotes the group —O-alkyl having preferably from approximately 1 to 20carbon atoms, more preferably from approximately 1 to 10 carbon atoms,for example 1, 2, 3, 4, 5, 6, 7, 8, 9 or 10 carbon atoms. These termsinclude all the configurations of the alkyl groups. According to aparticular embodiment, said alkyl group is a methyl group or an ethylgroup.

The term “aryl” includes especially the groups phenyl, naphthalyl andsimilar structures.

The expression “peptide or polypeptide having a given amino acidsequence” as used in the present application denotes a chain of several(at least two) successive amino acids forming the structure of a peptide(that is to say a chain of less than 20 amino acids) or of a polypeptide(that is to say a chain of more than 20 amino acids).

According to a particular embodiment, the peptide has a di-, tri- ortetra-peptide sequence, that is to say a sequence composed of two, threeor four successive amino acids.

According to a particular embodiment, the single amino acid is anaspartic acid (D or Asp) or said peptide or polypeptide comprises atleast one aspartic acid.

According to a particular embodiment, the compound of structure Icomprises an aspartic acid (D) and a valine (V or Val). By way ofexample, when said peptide or polypeptide has a dipeptide sequence, itssequence can be Valine-Aspartic acid (VD). In the case of a tripeptidepeptide or polypeptide, its sequence can be Valine-X-Aspartic acid (VXD)or Valine-Aspartic acid-Alanine (VD, for example Valine-Alanine-Asparticacid (VAD).

According to a particular embodiment, part B of the compound ofstructure I comprises or consists of the chain of amino acidsValine-Aspartic acid (VD). When it comprises other residues, said chaincan be followed and/or preceded by one or more (two, three, four, fiveor more than five) other amino acid(s), which can be of any type.

According to a particular embodiment, the compound of structure I isA-VD-C, in which A and C have any one of the definitions given in thepresent application, and more particularly the compound Q-VD-OPh.

According to a particular embodiment, the invention does not relate tothe compound Q-DEVD-OPH and/or to the compound Q-LEDH-OPH and/or to thecompound Q-IETD-OPH, taken as such.

According to a first embodiment, the single amino acid or at least oneof the amino acids of the peptide or polypeptide of the compound ofstructure I is O-methylated. When the single amino acid is an asparticacid or when the peptide or polypeptide comprises at least one asparticacid, said compound can in particular be O-methylated on the asparticacid or on at least one of its aspartic acids.

According to a second embodiment, the single amino acid or the aminoacid sequence of the peptide or polypeptide of the compound of structureI is not O-methylated. The absence of O-methylation is supposed toreduce the hydrophobicity of the peptide and facilitate its use in anaqueous medium.

According to a particular embodiment, R1 and/or R2 is(are) hydrogen.

According to a particular embodiment, R3 and/or R4 is(are) a fluoro.

According to a particular embodiment, the compound of structure Iaccording to the invention is a protease inhibitor, in particular acaspase inhibitor.

In the present application, the term “caspase” denotes any cysteineprotease as defined above.

“Protease inhibitor” or “caspase inhibitor” is understood as meaning anycompound which is capable of inhibiting the activation of at least oneprotease or the activation of at least one caspase, respectively, inparticular any compound which prevents or inhibits the process ofproteolytic cleavage which allows said protease or caspase to beobtained in active form. In particular, said caspase inhibitor preventsor inhibits the production of apoptogenic forms of the caspase inquestion. Demonstration of the inhibition (of the activation) of one ormore protease(s) and in particular of one or more caspases can becarried out, for example, by immunotransfer (Western blot) usingantibodies specific for different forms and proforms of said protease(s)or caspase(s) which are supposed to be inhibited by said inhibitor, asdescribed in FIG. 1 and in Example B-1. The inhibition of one or moreprotease(s) or caspase(s) can be total (in which case the active form ofsaid protease(s) or caspase(s) is not detected) or only partial (saidprotease(s) or caspase(s) is(are) then detected in active form but in areduced quantity as compared with the quantity detected in the absenceof the inhibitor).

According to a particular embodiment, the compound of structure Iaccording to the invention inhibits:

-   -   at least one caspase selected from the inflammatory caspases        (group I), in particular caspase-1, -4, -5, -11, -12, -13 and        -14, more particularly caspase-1 and -12; and/or    -   at least one caspase selected from the initiator caspases (group        II), in particular caspase-2, -8, -9 and -10, more particularly        caspase-8 and -10; and/or    -   at least one caspase selected from the effector caspases (group        Ill), in particular caspase-3, -6 and -7, more particularly        caspase-3.

According to a particular embodiment, the compound of structure Iinhibits a plurality of caspases (two, three, four or more than fourcaspases) of group I and/or of group II and/or of group III.

According to a particular embodiment, the compound of structure Iaccording to the invention is a broad-spectrum inhibitor, that is to sayit inhibits one or more caspase(s) from two groups selected from groupsI, II and III or from the three groups I, II and III.

According to a particular embodiment of the invention, the compound ofstructure I according to the invention or one of the compounds ofstructure I according to the invention is the compound of the followingformula:

According to a particular embodiment of the invention, the compound ofstructure I according to the invention or one of the compounds ofstructure I according to the invention is the O-methylated compoundQ-VD-OPh(N-(2(quinolyl)valyl-O-methyl-aspartyl-(2,6-difluorophenoxy)methylketone), the empirical formula of which is C27H27F2N3O6, or thenon-O-methylated compound Q-VD-OPh(N-(2-(quinolyl)valyl-aspartyl-(2,6-difluorophenoxy)methyl ketone), theempirical formula of which is C26H25F2N3O6. According to a particularembodiment of the invention, therefore, the compound of structure Iaccording to the invention or one of the compounds of structure Iaccording to the invention is the compound of the following formula:

The compound Q-VD-OPh is preferably in O-methylated form, thenon-O-methylated form generally being less stable than the O-methylatedform.

In the present application, “antiviral agent” and “antiretroviral agent”are understood as meaning, respectively, any agent (that is to say anyactive ingredient) having an antiviral or antiretroviral effect. Suchagents include in particular antiviral and in particular antiretroviralmedicaments which act on at least one step of the replication of thevirus. In particular, said agents can allow viral replication to beprevented, reduced or inhibited.

The present invention relates also to a composition, in particular apharmaceutical composition, comprising at least one compound ofstructure I as defined in the present application.

Accordingly, the compound according to the invention, which is used inthe prophylaxis and/or treatment of a viral infection, can becharacterized in that it is used in the production of a composition, inparticular a pharmaceutical composition (for example an antiviralcomposition). Where appropriate, said composition further comprises oneor more carrier(s), diluent(s) or adjuvant(s) or a combination thereof.

The compound of structure I according to the invention, like acomposition (in particular a pharmaceutical composition) or acombination (or kit) comprising said compound of structure I (seehereinbelow), can be administered to any animal or human likely tobenefit from such administration, in particular to any animal or humaninfected or likely to be infected by a virus as described in the presentapplication.

As used in the present application, the term “animal” defines anynon-human animal, in particular any non-human mammal, and moreparticularly an ape or a cat.

As used in the present application, the expressions “viral infection”and “infected by a virus” mean that said animal or human has beenexposed to a pathogenic RNA or DNA virus and that said virus hasattached itself to one or more cells of the host and has then penetrated(or is likely to penetrate) into said cell(s) and has had (or willpossibly have) harmful effects for at least one cell of said animal orhuman. In particular, such a viral infection is capable of evolving intoclinical signs of induced pathologies or pathologies accompanying saidinfection. Accordingly, a “viral infection” within the scope of thepresent invention includes the earliest phases of viral contamination aswell as the latest phases and the intermediate phases of viralcontamination. By way of example, in the case of HIV, the infectionevolves in several phases which may follow one another over time. Fourphases in particular are distinguished: (1) the primary infectioncorresponds to the phase of seroconversion which follows contaminationand is (in 50 to 75% of cases) or is not accompanied by symptoms; it isfollowed by (2) a latent phase, then (3) a phase with minor symptoms,and finally (4) the phase of profound immunodepression or the AIDSstage, which is generally symptomatic and is generally accompanied bynumerous opportunistic infections.

The term “viral infection” therefore also includes any clinical sign,symptom or disease that occurs in an animal or human (patient) followingcontamination of said animal or patient by a virus as described in thepresent application. Accordingly, the “viral infection” includes bothcontamination by said virus and the various pathologies which are theconsequence of contamination by said virus.

The viral infections which fall within the scope of the presentinvention include in particular the group constituted by viralencephalitis, viral meningitis, aphthous fever, influenza, yellow fever,respiratory viral infections, infantile diarrhoea, in particularinfantile diarrhoea caused by rotavirus, haemorrhagic fevers, inparticular haemorrhagic fevers caused by the Ebola virus, the denguevirus and the Lassa virus, poliomyelitis, rabies, measles, rubella,varicella, smallpox, herpes zoster, genital herpes, hepatitis,especially A, B, C, D and E, SARS, leukaemia and paralysis due to HTLV-1(human T lymphotropic virus type 1), as well as infections caused by anHIV virus, and more particularly by HIV-1 or HIV-2, or an SIV virus,which include in particular acquired immunodeficiency syndrome (AIDS).

The term “prophylaxis” denotes any degree of retardation in the time ofappearance of clinical signs or symptoms of the viral infection, as wellas any degree of inhibition of the severity of the clinical signs orsymptoms of the viral infection, including, but not being limited to,the total prevention of the viral infection. This requires the compoundof structure I according to the invention or the composition orcombination comprising said compound of structure I to be administeredto the animal or patient likely to be contaminated by a virus before anyclinical sign or symptom of the disease appears. The prophylacticadministration of the compound of structure I according to the presentinvention or of a composition or combination comprising said compoundcan take place before said animal or human is exposed to the virusresponsible for the viral infection, or at the time of exposure. Such aprophylactic administration serves to prevent and/or reduce the severityof any subsequent infection.

The above definition of the term “prophylaxis” also applies to theexpression “prevent an infection”.

“Treatment” is understood as meaning the therapeutic effect produced onan animal or human by the active substances (in particular the caspaseinhibitor(s) according to the invention) when they are administered tosaid animal or human at the time of contamination of said animal orhuman by the virus or after contamination. When the compound ofstructure I according to the invention or a composition or combinationcomprising said compound of structure I is administered to an animal orhuman after contamination by the virus, it can be administered duringthe primary infection phase, during the asymptomatic phase or after theappearance of clinical signs or symptoms of the disease. According to aparticular embodiment, administration takes place within 24 or 48 hoursof said animal or human being exposed to said virus, as quickly aspossible.

The term “treatment” includes any curative effect obtained by virtue ofthe compound of structure I according to the invention or a compositionor combination comprising said compound, and also the improvement in theclinical signs or symptoms observed in the animal or patient as well asthe improvement in the condition of the animal or patient. The termincludes in particular the effects obtained as a consequence ofinhibiting viral replication and/or inhibiting cell death induced by thevirus. Accordingly, the term “treatment” covers the slowing down,reduction, interruption and stopping of the viral infection and/or ofthe harmful consequences of the viral infection; treatment does notnecessarily require the complete removal of all the clinical signs ofthe viral infection and the symptoms of the disease, nor the completeelimination of the virus.

The definition of the term “treatment” also applies to the expression“treat an infection”.

The compound of structure I according to the invention or a compositionor combination comprising said compound of structure I can therefore beadministered to an animal or human at risk of developing a viralinfection (prophylaxis) or after contamination by the virus has takenplace, in particular after manifestation of the first clinical signs orsymptoms of the disease, for example after proteins or antibodiesspecific to said virus have been detected in the blood of the animal orpatient (treatment). According to a particular embodiment, treatment isstarted when the patient exhibits clinical signs of immunodepression orwhen the level of T lymphocytes, in particular TCD4+ lymphocytes, in asample of blood taken from the patient or animal is less than 350 permicrolitre, in particular less than 200 per microlitre.

According to a particular embodiment, therefore, the compound ofstructure I according to the invention or a composition or combinationcomprising said compound of structure I is administered to an animal orhuman before said animal or human is exposed to said virus, duringexposure to said virus or after exposure to said virus. Administrationafter exposure to the virus can be carried out at any time but willpreferably be carried out as quickly as possible after exposure, inparticular within 48 hours of the animal or human being exposed to saidvirus.

Furthermore, it is also possible to envisage a plurality of successiveadministrations of the compound of structure I according to theinvention or of a composition or combination comprising said compound,so as to increase the beneficial effects of the treatment. In order toincrease the chances of cure, or at least prolong the life expectancy ofthe animal or human, or the prophylactic effect, it is possible inparticular to carry out one or more successive administrations of saidcompound of structure I or of said composition or combination or of saidkit before the animal or human is exposed to the virus and/or duringexposure to the virus and/or after exposure to the virus, in particularwithin 48 hours of said animal or human being exposed to said virus.

The viruses that fall within the scope of the present invention includeDNA viruses and RNA viruses, in particular viruses responsible for celldeficiencies such as immune deficiencies (such as AIDS), neuronaldeficiencies (such as rabies) or epithelial deficiencies (such ashaemorrhagic fevers).

More specifically, said virus is a virus selected from the followingfamilies:

-   -   the flaviviridae, in particular those of the genus flavivirus,        which includes especially the dengue virus, the yellow fever        virus and the viruses responsible for viral encephalitises, such        as the West Nile virus, the Japanese encephalitis virus and the        Saint-Louis encephalitis virus;    -   the orthomyxoviruses, which include the influenza viruses;    -   the paramyxoviridae, in particular those of the genus        morbillivirus, especially the measles virus, and the respiratory        viruses, in particular those of the genus pneumovirus, for        example human respiratory syncytial virus and metapneumovirus;    -   the reoviridae, in particular the virus of the genus rotavirus;    -   the picornaviridae, in particular the viruses of the genus        enterovirus, including the polioviruses and the viruses        responsible for viral meningitis, those of the genus        aphthovirus, especially the aphthous fever virus, and those of        the genus rhinovirus;    -   the filoviridae, in particular the Ebola virus;    -   the arenaviridae, in particular the Lassa virus;    -   the rhabdoviridae, in particular those of the genus rhabdovirus,        including the rabies virus, and the genus vesiculovirus, which        includes the vesicular stomatitis virus;    -   the togaviridae, in particular of the genus Rubivirus, including        the rubella virus;    -   the poxviridae, in particular the vaccinia and variola viruses;    -   the herpesviridae, in particular the Herpes, varicella and        Zoster viruses;    -   the hepatitis viruses, especially the hepatitis A, B, C, D and E        viruses;    -   the coronaviridae, in particular the genus coronavirus, for        example the SARS virus;    -   the retroviruses, in particular those of the genus lentivirus        and those of the genus oncovirus, for example the HTLV-1 virus.

The present invention is directed in particular to the lentiviruses, inso far as they cause the degeneration of multiple organs.

According to a particular embodiment, said virus is a human retrovirus,in particular a human lentivirus, more particularly a humanimmunodeficiency (HIV) virus such as HIV-1 or HIV-2, and preferablyHIV-1.

According to another particular embodiment, said virus is a simianretrovirus, in particular a simian lentivirus, and more particularly asimian immunodeficiency virus (SIV) such as the SIVmac251 or SIVmac239virus or any other virus mentioned in Gordon et al.

The compound(s) of structure I according to the invention or acomposition or combination comprising the compound(s) of structure I canbe used to prevent, reduce and/or inhibit viral replication in an animalor human infected by a virus as defined above.

The term “viral replication” as used in the present application includesthe totality of the steps of the replication cycle of the virus, inparticular the main steps of replication of the retroviruses describedin the present application, including entry of the virus into the cell,integration of the viral genome into the DNA of the host cell, and viralmaturation.

“Viral maturation” or “maturation of the viruses” denotes, in the caseof the lentiviruses and in particular in the case of the HIV viruses,the process of cleavage of the Gag polyproteins, by the viral protease,into 4 structural proteins (p17, p24, p7 and p6) and the assembly ofthose proteins to the matrix (p17), capsid (TCD4+ p24) and nucleocapsid(p7). Following the maturation phase, the virions, which, prior tocleavage, were not mature, are infectious, that is to say ready toinfect new cells.

The prevention or inhibition of viral replication can be either partialor total.

According to a particular embodiment, the compound(s) of structure I ora composition or combination comprising it(them) has(have) the abilityto prevent, reduce and/or inhibit viral replication in vitro.

According to a particular embodiment, the compound(s) of structure Iis(are) the compound Q-VD-OPH or a derivative of the compound Q-VD-OPH(for example a compound of structure I in which part B consists of theamino acid chain VD), said derivative having retained the ability of thecompound Q-VD-OPH to prevent, reduce and/or inhibit viral replication invitro.

Advantageously, the effect tested in vitro is also obtained in vivo,under appropriate use conditions.

The ability of the compound of structure I according to the invention orof a composition or combination comprising said compound of structure Ito prevent or inhibit viral replication can be evaluated, for example,in vitro, by flow cytometry, after intracellular labelling of a viralantigen such as p24, as described in the examples below.

According to a particular embodiment, the compound of structure Iaccording to the invention or a composition or combination comprisingsaid compound of structure I is used to prevent, reduce and/or inhibitthe synthesis of viral proteins in an animal or human infected by avirus as described in the present application.

The expression “viral proteins” refers to at least one protein of thevirus, in particular to at least one structural protein of the virus.The viral proteins whose synthesis can be prevented, slowed, reducedand/or inhibited under the effect of the active ingredients according tothe invention, in particular under the effect of the compound(s) ofstructure I according to the invention, include in particular theenvelope, capsid, nucleocapsid proteins, etc., especially for thelentiviruses, the proteins Gag, Pol and Env.

The prevention or inhibition of the synthesis of viral proteins can bepartial, or total, or partial for some of the viral proteins and totalfor the remainder of the viral proteins. When it is partial for all theviral proteins or for some viral proteins, the expression “prevent orinhibit the synthesis of viral proteins” means that, under the effect ofone or more active substance(s) according to the invention, inparticular under the effect of one or more compound(s) of structure Iaccording to the invention, one or more viral proteins are synthesizedin a smaller quantity in the host cell, and are therefore present in asmaller quantity in the host cell or in the cell supernatant, ascompared with the synthesis of the same viral proteins in the absence ofsaid active substance(s). When the prevention or inhibition of thesynthesis of viral proteins is total, the viral protein(s) is(are) notsynthesized in a detectable manner.

The prevention or inhibition of protein synthesis can be evaluated, forexample, by immunotransfer (Western blot), using specific antibodiesdirected against said viral proteins, as described in Example B6 andFIG. 6.

The compound of structure I according to the invention or a compositionor combination comprising said compound can further be used forpreventing and/or inhibiting both (i) viral replication, in particularviral protein synthesis, and (ii) the increase in cell death, inparticular the increase in the death of the T lymphocytes and moreparticularly of the CD4+ T cells, induced by a virus as described in thepresent application, in an animal or human infected by said virus.

The compound(s) of structure I according to the invention or acomposition or combination comprising said compound(s) can be used inparticular in the treatment or prophylaxis of a viral infectionassociated with an increase in cell death, in particular an increase inthe death of the cells of the immune system and/or of the neuronal cellsand/or of the epithelial cells, in an animal or human infected by saidvirus. The invention is directed more particularly towards viralinfections correlated with an increase in the cell death of the T cells,and in particular the CD4+ T cells, in an animal or human infected by avirus, in particular infections by the HIV viruses.

An “increase in cell death” or an “increase in apoptosis” within thescope of the present application means that the percentage cell death isgreater than the percentage normally observed in the cell model inquestion. By way of example, in the case of normal (uninfected) CEMcells, there will be considered to be an increase in cell death when thepercentage cell death is greater than 1.7% (background noise observedaccording to Gandhi et al., 1998). Also by way of example, in a primaryculture of healthy activated CD4+ lymphocytes, there will be consideredto be an increase in cell death when the percentage cell death isgreater than 8% (background noise normally observed). According to aparticular embodiment, cell death or apoptosis increases by at least10%, at least 20% or at least 40%, or even more. This increase can bedemonstrated in vitro by any laboratory technique conventionally used toquantify the percentage cell death or apoptosis; for example, in thecase of cell death, a simple direct cell count using a microscope willbe sufficient. In the case of apoptosis, it is possible to use, forexample, the TUNEL (for “terminal deoxyribonucleotidyl transferase(TDT)-mediated dUTP-digoxigenin nick end labelling”) technique or tolabel the cells with acridine orange or measure mitochondrialdepolarization.

The expression “a viral infection associated with an increase in celldeath” and in particular “a viral infection associated with an increasein apoptosis” is understood as meaning an infection which is generallyaccompanied, in the more or less long term, by an increase in cell deathand in particular in apoptosis. The increase can be the direct and/orindirect result of contamination by a virus as described in the presentapplication.

Prevention or inhibition of the increase in cell death or apoptosis canbe partial or total. When it is partial, the expression “prevent and/orinhibit the increase in cell death” or “prevent and/or inhibit theincrease in apoptosis” means that, under the effect of one or moreactive substance(s) according to the invention, in particular under theeffect of one or more caspase inhibitor(s) according to the invention,the number of dead cells or the number of apoptotic cells in the hostorganism or in certain tissues or for certain particular cell types ofthe host organism is reduced relative to the number observed in theabsence of said active substance(s). Cell death is reduced preferably byat least 10%, more preferably at least 30% and yet more preferably atleast 50%.

According to a particular embodiment, the compound of structure Iaccording to the invention can be prepared in the form of apharmaceutical composition further comprising one or more carrier(s),diluent(s) and/or adjuvant(s) or a combination thereof, as well as otheractive substances. In the case of an injectable administration, therecan be chosen especially a formulation in an aqueous, non-aqueous orisotonic solution.

In the present application, the term “carrier” denotes any substrate(that is to say anything which is able to transport at least one activeingredient) which does not interfere with the efficacy of the biologicalactivity of the active substances (in particular the compound(s) ofstructure I). A large number of carriers are known in the prior art. Thecarriers used can be, for example, water, a saline solution, serumalbumin, a Ringer solution, polyethylene glycol, water-misciblesolvents, sugars, binders, excipients, pigments, vegetable or mineraloils, water-soluble polymers, surface-active agents, thickening orgelling agents, cosmetic agents, solubilizing agents, stabilizingagents, preservatives, alkalinizing or acidifying agents or acombination thereof. The formulation of such carriers in the form of apharmaceutical composition is described especially in “Remington'sPharmaceutical Sciences”, 18th edition, Mack Publishing Company, Easton,Pa.

In the present application, the term “diluent” means a diluting agentand includes soluble diluents and insoluble diluents. There is generallyused an insoluble diluent when the active ingredient is soluble and asoluble diluent when the active ingredient is insoluble. An “insoluble”active ingredient can be completely insoluble in an aqueous medium orcan have limited solubility (that is to say a solubility of less than 10mg/ml in 250 ml of water at a pH of from 1.0 to 7.5) in an aqueousmedium. Examples of insoluble diluents include microcrystallinecellulose, silicified microcrystalline cellulose,hydroxymethylcellulose, dicalcium phosphate, calcium carbonate, calciumsulfate, magnesium carbonate, tricalcium phosphate, etc. Examples ofsoluble diluents include mannitol, glucose, sorbitol, maltose,dextrates, dextrins, dextrose, etc.

The adjuvants which can be used within the scope of the invention are inparticular nucleic acids, peptidoglycans, carbohydrates, peptides,cytokines, hormones or other small molecules. Said adjuvants that areused can be, for example, adjuvants of the non-methylated CpGdinucleotide (CpG) family, adjuvants of the poly IC family and adjuvantsof the monophosphoryl lipid A (MPL) family or an analogue thereof.

According to a preferred embodiment, the carrier(s) or diluent(s) orcombinations thereof used in the invention are pharmaceuticallyacceptable substances or a combination of pharmaceutically acceptablesubstances. A substance or a combination of substances is said to be“pharmaceutically acceptable” when it is suitable for administration toa living being (for example a human or animal) for therapeutic orprophylactic purposes. It is therefore preferably non-toxic for the hostto which it is administered.

The terms “administration” and “administer” as used in the presentapplication include any administration, whatever the chosen route ofadministration.

The routes of administration and the dosages vary according to a varietyof parameters, for example according to the condition of the patient,the type of infection and the severity of the infection to be treated,or according to the compound(s) of structure I and the other antiviralagents used.

The compound of structure I according to the invention, the compositionaccording to the invention (in particular the antiviral compositionaccording to the invention) and the constituents of the combinationaccording to the invention can especially be administered to an animalor human in dry form, in solid form (in particular tablet, powder,gelatin capsule, pill, granules, suppository, polymer capsule orcompressed tablet, and more precisely accelerated release tablet,enteric-coated tablet or sustained release tablet), in gel form or inthe form of a solution or liquid suspension (in particular syrup,injectable, infusible or drinkable solution, microvesicles, liposomes).The compounds can also be in the form of doses in dry form (powder,lyophilisate, etc.) for reconstitution at the time of use using asuitable diluent.

According to their galenical form, the composition according to theinvention (in particular the antiviral composition of the invention) andthe constituents of the combination of the invention can be administeredby the enteral, parenteral (intravenous, intramuscular or subcutaneous),transcutaneous (or transdermal or percutaneous), cutaneous, oral,mucosal, in particular transmucous-buccal, nasal, ophthalmic, otological(in the ear), oesophageal, vaginal or rectal route, or alternatively bythe intragastric, intracardiac, intraperitoneal, intrapulmonary orintratracheal routes.

In addition, the compound of structure I, the composition of theinvention or the constituents of the combination of the invention can bepackaged for administration in the form of a single dose (monodose) or amultiple dose (multidose). In order to increase the effects of thetreatment, it is possible to carry out administration in the form of aplurality of successive administrations, repeated on one or moreoccasions, after a particular time interval. For example, a plurality ofadministrations can be carried out per day or per week.

The amount of active ingredient administered to an animal or human is atherapeutically effective amount. A “therapeutically effective amount”is an amount sufficient to obtain a significant effect and in particularto bring a significant benefit to a human or animal within the scope ofan administration for prophylaxis or treatment as defined in the presentapplication. A therapeutically effective amount is also an amount forwhich the beneficial effects outweigh any toxic or harmful effect of theactive ingredient(s). Such an amount can correspond to an amountsufficient to significantly inhibit viral replication or to bring aboutthe disappearance, reduction or improvement of any existing infectioncaused by a virus. The therapeutically effective amount varies accordingto factors such as the state of infection and the age, sex or weight ofthe animal or human individual. The dosage regimens can be adjusted inorder to obtain an optimum therapeutic effect. For example, it ispossible to administer from 15 to 50 mg/kg body weight of compound ofstructure I according to the invention. More specifically, in the caseof a human weighing about 60 kg, a therapeutically effective amount ofcompound of structure I according to the invention can be from 100 to300 mg/day, administered in from 1 to 3 doses.

The present invention relates also to the use of one or more compound(s)of structure I, in particular the use of the compound Q-VD-OPh, inassociation with other antiviral agents, in particular otherantiretroviral agents, in the prophylaxis and/or treatment of a viralinfection. As examples of antiviral agents there may be mentioned, inconnection with infection due to HIV, the combined antiretroviral drugswithin the scope of highly active antiretroviral therapy (or “HAART”).

Accordingly, a particular pharmaceutical composition according to theinvention further comprises at least one other antiviral agent.

The present invention therefore relates also to a novel antiviralcomposition comprising, consisting essentially of or consisting of:

-   -   (i) at least one compound of structure I as defined in the        present application,    -   (ii) at least one other antiviral agent.

The compound of structure I can therefore be used in association with anantiviral agent or a plurality of antiviral agents, in particular atleast two other antiviral agents. Said other antiviral agent or agentscan in particular be antiretroviral agents.

The expression “consists essentially of” as used in the presentapplication means that other minor ingredients or molecules can bepresent with the active ingredients expressly listed, without affectingthe activity of said active ingredients.

The antiviral and antiretroviral agents which can be used within thescope of the present application include in particular:

-   -   transcriptase inhibitors, in particular reverse transcriptase        inhibitors, for the retroviruses, which are intended to act at        the very start of the viral replication cycle, especially        reverse transcriptase inhibitors which are intended to act        before the viral DNA becomes integrated into the DNA of the host        cell and which prevent or inhibit the synthesis of proviral DNA        from the viral RNA;    -   viral protease inhibitors (or antiproteases), which generally        act at the end of the viral cycle, during maturation of the        newly synthesized viral proteins;    -   inhibitors of the fusion of the viral envelope with the cell        membrane, which are intended to block the penetration of the        virus into the cell;    -   inhibitors of receptors or coreceptors, such as CD4 or BOB;    -   antisense oligonucleotides;    -   integrase inhibitors; and    -   molecules that target other steps of viral multiplication        (addressing, integration port).

According to a particular embodiment, said other antiviral agent oragents consist(s) of at least one transcriptase inhibitor and/or atleast one viral protease inhibitor.

According to a particular embodiment, the antiviral compositionaccording to the invention comprises, consists essentially of orconsists of:

-   -   (i) at least one compound of structure I according to the        invention,    -   (ii) at least one transcriptase inhibitor, and    -   (iii) at least one viral protease inhibitor.

The term “transcriptase inhibitor” as used in the present applicationincludes in particular the nucleoside analogues, the non-nucleosideanalogues and the nucleotide analogues of reverse transcriptase.

According to a particular embodiment, the transcriptase inhibitor is areverse transcriptase inhibitor, in particular an HIV virus reversetranscriptase inhibitor, and more particularly a reverse transcriptaseinhibitor selected from the group constituted by:

-   -   the nucleoside reverse transcriptase inhibitors of HIV, in        particular zidovudine or azidothymidine (AZT), didanosine or        ddl, zalcitabine or ddC, stavudine or d4T, lamivudine or 3TC,        abacavir or ABC, and emtricitabine or FTC;    -   the non-nucleoside reverse transcriptase inhibitors of HIV, in        particular nevirapine, efavirenz and delavirdine; and    -   the nucleotide analogues of the reverse transcriptase of HIV, in        particular tenofovir or bis-POC-PMPA.

According to a particular embodiment, one of the transcriptaseinhibitors used is AZT.

The term “protease inhibitor” as used in the present applicationincludes in particular peptidomimetic molecules and molecules of thenon-peptide type. “Peptidomimetic molecules” are peptides which mimicthe natural enzyme substrate and fix to the protease substrate bindingsites, preventing cleavage of the protein precursors (for example Gagand Gag-Pol for HIV or SIV), which leads to the production of defectiveand non-infectious viral particles.

According to a particular embodiment, the viral protease inhibitor is aprotease inhibitor of an HIV virus and in particular a viral proteaseinhibitor selected from the group constituted by the followingpeptidomimetic molecules: Indinavir or IDV, Nelfinavir or NLFN,Saquinavir or SQN, Ritonavir or RTN, Amprenavir, Lopinavir. According toa particular embodiment, one of the HIV viral protease inhibitors usedis Indinavir.

According to a particular embodiment, at least one of the otherantiviral agents according to the invention is a fusion inhibitor, inparticular an HIV virus fusion inhibitor, for example enfuvirtide. A“fusion inhibitor” is understood as being an inhibitor which acts in thefirst stage of replication of the virus by preventing fusion between theviral envelope and the cell membrane, for example by competitiveinhibition.

According to a particular embodiment, said antiviral composition canfurther comprise one or more carrier(s), diluent(s) and/or adjuvant(s)or a combination thereof as defined in the present application.

According to a particular embodiment, at least two compounds of theantiviral composition or of the combination according to the inventionact in “synergy”. This means that it is possible by means of saidantiviral composition or said combination to obtain a prophylactic ortherapeutic effect that is superior to the sum of the individual effectsof each of the compounds acting in synergy.

According to a particular embodiment, the compound(s) of structure I andat least one of the other antiviral agents act in synergy and, inparticular, the compound(s) of structure I act(s) in synergy with atleast one of the other antiviral agents. The results presented in thepresent invention show that a compound such as Q-VD-OPh is capable ofacting in synergy with other antiviral agents, and in particular withAZT and with Indinavir, to inhibit viral replication and to inhibit thedeath of the CD4+ T lymphocytes induced by the viral infection.

The use of a compound of structure I, in particular the use of thecompound Q-VD-OPh, or of a composition or combination comprising such acompound can therefore enable a treatment based on one or more otherantiviral agents, in particular an antiviral treatment that is not veryeffective against HIV or SIV viruses, to be improved or potentiated. Theterm “potentiate” means that the use of one or more compounds ofstructure I according to the invention makes it possible to obtain aprophylactic or therapeutic effect that is superior to the prophylacticor therapeutic effect obtained using said other antiviral agent(s) aloneor in combination with other medicament regimes.

In so far as the compounds of structure I are able to potentiate theeffect of other antiviral agents, and even act in synergy with saidother antiviral agent(s), the use of one or more compounds of structureI can also allow the doses of other antiviral agents that are used to bereduced without reducing the efficacy of the treatment, and even whileincreasing the efficacy of the treatment.

Another aspect of the present invention relates, therefore, to the useof one or more compound(s) of structure I, in particular the use of thecompound Q-VD-OPh, in the production of a medicament for potentiating,for increasing a prophylactic or therapeutic effect of one or more otherantiviral agents as defined in the present application and/or forreducing the amount of the other antiviral agents administered to ahuman or animal.

The present invention relates also to a compound of structure I, inparticular the compound Q-VD-OPh, for use in potentiating, in increasinga prophylactic or therapeutic effect of one or more other antiviralagents as defined in the present application and/or in reducing theamount of the other antiviral agents administered to a human or animal.

According to another aspect of the present invention, the activeingredients are combined in a combination (or kit) for use in anantiviral therapy.

Accordingly, the present invention relates also to a combination (orkit) comprising, consisting essentially of or consisting of:

-   -   (i) at least one compound of structure I and    -   (ii) at least one other antiviral agent, in particular at least        one other antiretroviral agent, in which compounds (i) and (ii)        are separate from one another. Compounds (i) and (ii) of said        combination are as defined in the present application. They can        be administered to the human or animal body simultaneously        and/or sequentially, separately in terms of time. It is in fact        possible that some constituents of said combination do not        necessarily exert their common activity simultaneously or        immediately.

The expression “combination” (or kit) refers to the association, in theposology of a treatment intended for a human or animal infected by avirus, of at least two compounds suitable for use in an antiviraltreatment in an animal or human:

-   -   (i) at least one compound of structure I and    -   (ii) at least one other antiviral agent as defined in the        present application.

Constituents (i) and (ii) form a functional unit by virtue of a commonindication, which is the implementation of an antiviral treatment.

The combination can also comprise a plurality of compounds of structureI, for example 2, 3 or 4 or more, and/or a plurality of other antiviralagents, in particular 2, 3, 4 or more.

Such a combined therapy is intended most particularly for theprophylaxis and/or treatment of viral infections in a human or animalinfected by a virus as defined in the present application.

The term “simultaneously” and the expression “simultaneousadministration” mean that compounds (i) and (ii) of said combination areadministered at the same time, at the same moment, to a human or animal.

According to a particular embodiment, compounds (i) and (ii) of saidcombination are present in two distinct compositions. “Present in twodistinct compositions” is understood as meaning that said compounds arephysically separate. They are then employed, administered separately,without prior mixing, in several (at least two) dosage forms (forexample two distinct capsules). Said combination therefore correspondsto a presentation of the compound(s) (i) on the one hand and of thecompound(s) (ii) on the other hand, in distinct compositions. Becausecompound(s) (i) is(are) not mixed with compound(s) (ii), the differentcompounds (i) and (ii) are not chemically modified and can consequentlybe administered as described in the notice(s) of compliance (AMM)covering the compound(s).

In the case where compounds (i) and compounds (ii) are administeredsequentially in terms of time, the sequence of administration is notimportant, it being possible for administration of compound(s) (i) toprecede or follow administration of compound(s) (ii). According to aparticular embodiment, compound (i) or at least one of compounds (i) isadministered before compound (ii) or at least one of compounds (ii) isadministered. Alternatively, compound (ii) or at least one of compounds(ii) can be administered before compound (i) or at least one ofcompounds (i) is administered.

The expression “sequential administration” means that said or one ofsaid compounds (i) and said or one of said compounds (ii) of thecombination or kit according to the invention are administered notsimultaneously but separately in terms of time, one after the other.

The term “precede” or “preceding” is used when a compound (or aplurality of compounds) of the combination or kit according to theinvention is administered a few minutes or several hours, or evenseveral days, prior to administration of the other compound(s) of saidcombination or kit. Conversely, the term “follow” or “following” is usedwhen a compound (or a plurality of compounds) of the combination or kitaccording to the invention is administered a few minutes or severalhours, or even several days, after administration of the othercompound(s) of said combination or kit.

Furthermore, according to a particular embodiment, compounds (i) and(ii) of the combination or kit according to the invention are formulatedfor administration at an interval of one or several hours, preferably a1-, 2-, 3- or 4-hour interval, more preferably a 1- or 2-hour interval,yet more preferably a 1-hour interval.

The compound(s) (i) and the compound(s) (ii) of the combination can beformulated to facilitate their ingestion and, in particular, can beformulated with one or more carrier(s), diluent(s) or adjuvant(s) asdefined above, or a combination thereof.

In addition, the compound(s) (i) and the compound(s) (ii) of thecombination or kit according to the invention can be administered by thesame route of administration or, on the other hand, by distinct routesof administration. The possible galenical forms and routes ofadministration are those described above.

According to a particular embodiment, said other antiviral agent(s)consist(s) of at least one transcriptase, especially reversetranscriptase, inhibitor as defined in the present application and/or atleast one viral protease inhibitor as defined in the presentapplication.

Preferably, at least two other antiviral agents are used. According to aparticular embodiment, therefore, the composition according to theinvention comprises:

-   -   (i) at least one compound of structure I according to the        invention,    -   (ii) at least one transcriptase inhibitor, and    -   (iii) at least one viral protease inhibitor.

The present invention relates also to an antiviral composition or acombination according to the invention for use as a medicament, inparticular as an antiviral agent and more particularly as anantiretroviral agent. More precisely, said antiviral composition or saidcombination can be used in the prophylaxis and/or treatment of a viralinfection, in particular an infection caused by a virus as defined inthe present application, and more particularly for inhibiting viralreplication, in a mammal or human.

The present invention relates also to the use of an antiviralcomposition or of a combination according to the invention in theproduction of a pharmaceutical composition for the prophylaxis and/ortreatment of a viral infection, in particular an infection caused by avirus as defined in the present application, in a mammal or human.

The invention relates also to a method of treating an animal or humaninfected by a virus as described in the present application, said methodcomprising at least one step of administration of the compound(s) ofstructure I according to the invention, of the antiviral compositionaccording to the invention or of the constituents of the combinationaccording to the invention.

Said treatment method is, in particular, suitable for and intended foruse in the prophylaxis and/or treatment of a viral infection, inparticular in a human or animal infected by a virus as defined in thepresent application.

More precisely, said treatment method can be used to prevent and/orinhibit viral replication in an animal or human infected by a virus.

Furthermore, said treatment method can be used to prevent and/or inhibitthe increase in cell death in an animal or human infected by a virus, inparticular the increase in the death of the T lymphocytes and moreparticularly the increase in the death of the CD4 T lymphocytes.

The treatment method according to the invention is considered to haveachieved the expected therapeutic effect if it permits a reduction of atleast 10%, preferably 30%, and more preferably at least 50%, in viralreplication in the treated animal or human. The therapeutic effect canalso be defined in relation to the clinical standards developed formeasuring the beneficial effects of medicaments on HIV infection. A drughas a beneficial effect if it halves the plasma viral load in humans. Adrug has a super-beneficial effect if it divides the plasma viral loadin humans by 100.

DESCRIPTION OF THE DRAWINGS

FIG. 1: Immunoblot (Western blot) showing the effectiveness of Q-VD-OPhin inhibiting activation of caspase-3 and -8. CD4⁺ T lymphocytes were orwere not infected by the HIV-1 virus (incubation: 2 hours) and thenstimulated by Concanavalin A and IL-2 (incubation: 2 hours). Afterstimulation, the inhibitor Q-VD-OPh was added to the cell culture at afinal concentration of 10 μM and then also added 36 hours afterinfection (d3) and 96 hours after infection (d4). The immunoblot wascarried out on the 6th day post-infection. Caspase-3 and -8 weredetected using the anticaspase antibodies indicated above. NI: controlcells (CD4⁺ T cells not infected by HIV-1 and not treated withQ-VD-OPh); HIV: CD4⁺ T cells infected by HIV-1 but not treated withQ-VD-OPh; HIV+QVD: CD4⁺ T cells infected by HIV-1 and then cultivated inthe presence of 10 μM of Q-VD-OPh. Actin serves as the control for theprotein load of the gel. The molecular weight marker RPN 800 (Amersham)was used.

FIG. 2: Analysis of the CD4+ T lymphocytes by flow cytometry on the 5thday after infection by HIV-1 and after stimulation by Concanavalin A andIL-2. A. Analysis of the size and granulometry of the CD4+ Tlymphocytes. B. Determination of the percentage of CD4+ cells having amitochondrial impairment (ΔΨm). C. Determination of the percentage ofCD4+ cells infected by HIV after intracellular labelling of the p24viral antigen. NI: uninfected CD4+ T lymphocytes; HIV: CD4+ Tlymphocytes infected by HIV-1; HIV Q-VD-OPh: CD4+ T lymphocytes infectedby HIV-1 (incubation: 2 hours), activated by ConA and IL2 (incubation 2hours) and then incubated with Q-VD-OPh (10 μM final); Q-VD-OPh is added36 hours (day 3) and 96 hours (day 4) after the start of the infection.

FIG. 3: Immunoblot (Western blot) showing the effect of Q-VD-OPh onmitochondrial damage resulting from viral replication. Primary CD4+ Tcells were infected with HIV-Lai and stimulated with a ConA/IL-2cocktail and then treated or not treated with 10 μM of Q-VD-OPh (QVD)and/or 10 μM of pepstatin A (PA) immediately after stimulation and then36 hours (day 3) and 96 hours (day 4) after infection. On the 5th daypost-infection, the cells were fractionated into two parts: the membranefraction and the cytosol fraction. The relocalization of the apoptogenicfactors Cytochrome c (Cyt c), Smac/Diablo and Endonuclease G (EndoG) wasthen evaluated by immunotransfer (Western blot). The proteins Cytochromec, Smac/Diablo and EndoG were detected using the antibodies indicatedabove. The proteins Cox IV and actin detected by means of theanti-subunit IV antibodies (clone 1068 Molecular Probe) and anti-actinantibodies (SIGMA), respectively, were used as the control for thefractionation procedure and as the control for the protein load of thegel, respectively.

FIG. 4: Graphic representation showing the effect of Q-VD-OPh onreplication of the HIV-1 virus. A. Determination of the percentage ofCD4+ T lymphocytes infected by HIV-1 by flow cytometry, afterintracellular labelling of the p24 viral antigen. B. ELISA assay of thep24 viral antigen in the culture supernatants. All the cells werestimulated by Con A and IL2 within 24 hours of infection. The parameterswere measured on the 6th day post-infection. NI: uninfected CD4+ Tlymphocytes; HIV: CD4+ T lymphocytes infected by HIV-1; HIV+QVD andHIV+PA+QVD: CD4+ T lymphocytes infected by HIV-1, to which there wereadministered, on the 3rd day post-infection and then every day, Q-VD-OPh(QVD) or Q-VD-OPh (QVD) and pepstatin A (PA), respectively.

FIG. 5: The time at which Q-VD-OPh is administered to the CD4+ Tlymphocytes influences the inhibition of cell death and the inhibitionof viral replication. CD4+ T lymphocytes were or were not infected withHIV-Lai and stimulated with a ConA/IL2 cocktail and then treated or nottreated with 10 μM of Q-VD-OPh and/or 10 μM of pepstatin A. There weredetermined, by flow cytometry, the percentage of CD4+ T lymphocytesinfected by HIV after intracellular labelling of the p24 antigen (A) andthe percentage of dead CD4+ T lymphocytes (B) on the 5th day afterinfection by HIV-1. The parameters were measured on the 5th daypost-infection. NI: CD4+ T lymphocytes not infected by HIV-1; HIV: CD4+T lymphocytes infected by HIV-1; Q-VD: CD4+ T lymphocytes infected byHIV-1, to which there were administered Q-VD-OPh and pepstatin A (PA);in the first case (Before), Q-VD-OPh and PA were administered between 1and 2 hours before infection by HIV-1 and stimulation by Concanavalin Aand IL-2 and then on d3 and d4 post-infection, at a final concentrationof 10 μM. In the second case (After), Q-VD-OPh and PA were administeredimmediately after infection by HIV-1 and on d3 and d4 post-infection atdifferent final concentrations (0.5; 1; 2; 5; 10 and 20 μM).

FIG. 6: Immunoblot (Western blot) showing the inhibitory effect ofQ-VD-OPh on the expression of a group of HIV-1 proteins in primary CD4+cells. Protein extracts prepared on the 6th day of culturing fromuninfected CD4+ T lymphocytes (NI) or CD4+ T lymphocytes infected by theHIV-1 virus and then cultivated in the absence of Q-VD-OPh (HIV) or inthe presence of Q-VD-OPh (HIV+Q-VD-OPh) were fractionated into threeparts: the cytosol fractions (cytosol), the soluble membrane fractions(soluble) and the insoluble membrane fractions (insoluble). Q-VD-OPh wasadded at a final concentration of 10 μM, immediately after infection andthen 36 hours (d3) and 96 hours (d4) post-infection. The proteinsspecific to HIV were detected using a mixture of sera from HIV+patients.They are indicated on the right of the immunoblot. The molecular weightmarker RPN 800 (Amersham) was used.

FIG. 7: Graphic representation showing the effect of Q-VD-OPh on primaryHIV-1 strains. In all cases (A, B and C), the CD4+ T lymphocytes werestimulated with concanavalin A and IL2 (stimulation being carried outbefore or during administration of Q-VD-OPh), and Q-VD-OPh was added ata final concentration of 10 μM, immediately after infection and then 36hours (d3) and 96 hours (d4) post-infection. A. Analysis by flowcytometry of viral replication in CD4+ T lymphocytes infected with theHIV-1Lai virus or with the serum of a chronic HIV+ patient (strain withX4/R5 dual tropism) and then cultivated in the absence or presence(+Q-VD) of Q-VD-OPh. The percentage of CD4+ cells infected by HIV wasdetermined after intracellular labelling of the p24 viral antigen on the5th day post-infection in the case of the HIV-Lai virus and on the 6thday post-infection in the case of the serum. PE: phycoerythrin,fluorochrome (emission at 578 nm) coupled to the anti-p24 antibody. B.Quantification of viral replication (on the left) and of cell death bymeasurement of mitochondrial depolarization (on the right) in CD4+ Tlymphocytes infected with the serum of the chronic HIV+ patient. C.Analysis of the replication of five viral isolates from HIV+ patients,with R5 tropism, in the absence (−) or in the presence (+) of Q-VD-OPhor of a final concentration of 1 μM of didanosine (ddl, SIGMA), areverse transcriptase inhibitor also called Vivex EC® (Bristol-MyersSquibb).

FIG. 8: Graphic representation showing the inhibitory effect of Q-VD-OPhon replication of the SIVmac251 virus and the formation of syncitia. Thecell line CEMx174 was infected with 200 AID50 (infectious dose necessaryfor 50% of the animals to be infected) of the strain SIVmac251. Twohours after infection, the cell line was treated with differentconcentrations of inhibitor Q-VD-OPh (final concentration of 20, 10 or2.5 μM) or was not treated (0 μM). On the 4th and 5th dayspost-infection, viral production in the culture supernatant wasevaluated by RT-PCR (Taqman) and the number of syncytia was evaluatedusing an optical microscope.

FIG. 9: Graphic representation showing a synergistic effect of Q-VD-OPhwith AZT and Indinavir. Primary CD4+ T cells infected by the HIV-Laivirus and then stimulated with concanavalin A and IL-2 were treated 96hours after infection with different concentrations of Q-VD-OPh (0, 0.1,1 and 10 μM) in the absence or presence of azidothymidine (AZT; 0.1 μM)or Indinavir (IND; 1 μM). Inhibition of cell death was quantified byflow cytometry on the 5th day post-infection. It is expressed asfollows:

(% cell death induced by HIV in the absence of treatment−% cell deathinduced by HIV in the presence of treatment)/(% cell death induced byHIV in the absence of treatment−% cell death in the control)×100.

FIG. 10. Analysis by flow cytometry of the fall in the mitochondrialtransmembrane potential (% Δφm low) starting from Jurkat cells incubatedin the absence or presence of different concentrations of anti-CD95 (A)and in the absence or presence of 0.25 μg/ml of anti-CD95 and ofdifferent caspase inhibitors (B). C. Analysis by immunoblot of Jurkatcell extracts treated in the presence or absence of anti-CD95 and ofdifferent caspase inhibitors.

FIG. 11. Analysis by flow cytometry of the internal viral protein p24(A) and of the fall in the mitochondrial transmembrane potential (% Δφmlow; B) on the 5th (d5) and 7th (d7) day post-infection in primary CD4+T cells infected by the strain HIV-Lai, after stimulation byConcanavalin A and IL-2 and in the presence or absence of 10 μM ofdifferent caspase inhibitors.

FIG. 12. Analysis by immunoblot of the quantity of HIV viral proteinsproduced from extracts of primary CD4 T cells infected by the strainHIV-Lai in the presence or absence of different caspase inhibitors.

FIG. 13. Analysis by flow cytometry of lymphocyte proliferation after 4and 5 days' stimulation by 1 μg/m1 of anti-CD-3, in the presence orabsence of HIV antiproteases or of QVD-OPH.

FIG. 14. Analysis of the fall in the mitochondrial transmembranepotential (% Δφm low) by flow cytometry starting from cells stimulatedby 1 μg/ml of anti-CD-3 in the presence or absence of different HIVantiproteases and of QVD-OPH.

FIG. 15. Analysis of the fall in the mitochondrial transmembranepotential (% Δφm low) by flow cytometry in monocytes and lymphocytes inthe presence of different HIV antiproteases or of QVD-OPH.

EXAMPLES Example 1 Analysis of the Properties of Q-VD-OPh A. Materialand Methods

Antibodies

For the immunoblots (Western blot): anti-Smac/Diablo rabbit polyclonalantibodies (ΨProSci), anti-endonuclease-G (ΨProSci), anticaspase-3(Stressgen), antiactin (Sigma), anticaspase-8 monoclonal antibodies(Cell Signaling), anti-Cytochrome c clone 7H78.2C12 (BD Pharmingen),anti-Cox IV, subunit IV, clone 10G8 (Molecular Probes).

For cytofluorometry: anti-p24 monoclonal antibody, clone KC57-RD1(Beckman coulter).

Synthetic Inhibitors

Cathepsin D inhibitor: pepstatin A (Sigma).

Broad-spectrum caspase inhibitor: Q-VD-OPh in non-O-methylated form(N-(2(quinolyl)valyl-aspartyl-(2,6-difluorophenoxy)methyl ketone; EnzymeSystem Products, MP Biomedicals.

Reverse transcriptase inhibitor: didanosine (or ddl) or Videx EC®(Bristol-Myers Squibb).

Isolation of CD4⁺ Cells and Culture Conditions

Peripheral blood mononuclear cells obtained from healthy volunteers(Etablissement Francais du sang) were isolated on Ficoll strains (Petitet al., 2002). The majority of the adherent cells were eliminated byincubation in plastics culture dishes. The circulating CD4⁺ cells wereselected negatively using a CD4⁺ cell isolation kit, in accordance withthe supplier's instructions (MACS, CD4 T cell isolation kit II; MiltenyiBiotech, Paris, France). The purity of the isolated CD4⁺ population,determined by flow cytometry, was ≧96%. Monocytes recovered from theadherent dishes were added to the purified CD4⁺ cells in a finalpercentage of 6%. The composition of the culture medium used is asfollows: RPMI 1640, 10% foetal calf serum, 2 mM glutamine, 1 mMpyruvate, 50 units/ml of penicillin and 50 μg/ml of streptomycin.

Measurement of Viral Replication

The CD4⁺ cells were incubated for 2 hours at 37° C. in the presence of10 ng/ml of HIV-1 virus of strain Lai or 50 ng/ml of primary strains ofthe HIV-1 virus. After 2 washings, the cells were resuspended in acomplete medium in the presence of 5 μg/ml of concanavalin A (Con A) and10 mg/ml of interleukin 2 (IL 2). The HIV p24 antigen, the control forthe viral load, was measured in the cell culture supernatants by anELISA test (Abbott). The intracellular p24 antigen was determined byflow cytometry with the aid of a specific antibody (KC57, Coulter Corp)and after permeabilization of the cells using the permeabilizationreagent Intraprep (Coulter Corp.).

Measurement of Cell Death and Analysis by Flow Cytometry

In order to evaluate the change in the transmembrane potential of theinner mitochondrial membrane (Δφm), the CD4⁺ cells were labelled for 15minutes at 37° C. with 40 nM of DIOC₆ (3-3′-diethyloxacarbocyanine). Thedead cells exhibit a reduction in labelling intensity. The size andmorphometry were also determined. The apoptotic/dead cells were countedby white-light microscopy, on the basis of abnormal cell morphologyand/or the absorption of trypan blue.

Immunoblot (Western Blot)

20 μg extracts of each of the cytosol and mitochondrial fractions wereboiled for 5 minutes in Laemmli buffer containing 2% SDS and 10%2-β-mercaptoethanol and then migrated onto 10-20% polyacrylamidegradient gels (Bio-Rad). After transfer of the proteins to apolyvinylidene difluoride membrane (Bio-Rad), the immunoblots wereincubated with the primary and post-secondary antibodies coupled tohorseradish peroxidase, obtained from Amersham Biosciences (Orsay,France). They were subsequently developed and revealed bychemiluminescence (ECL from Amersham or West Femto from Pierce) using aCCD camera (Fuji LAS-1000plus) and L process software from Science Lab(Isochem, Paris, France).

Subcellular Fractionation

The cytosol and mitochondrial fractions were obtained by the subcellularfractionation technique based on selective permeabilization by digitoninaccording to Foghsgaard et al. {Foghsgaard, 2001}. Briefly, 10⁷ cellswere washed twice in PBS and incubated for 5 minutes on ice with 100 μlof extraction buffer (35 μg/ml digitonin, 250 mM sucrose, 137 mM NaCl,70 mM KCl, 4.3 mM Na₂HPO₄, 1.4 mM KH₂PO₄, 2 mM EDTA, pH 7.2)supplemented with a protease inhibitor cocktail (“Complete” from RocheApplied Science, Penzberg, Germany). The extracts were centrifuged at300 g for 5 minutes, and the resulting supernatant was recentrifugedagain at 10,000 g for 10 minutes at 4° C. in order to remove the debris.The final supernatant, called the cytosol fraction, was stored at −80°C. The pellet was dissolved in 100 μl of mitochondrial lysis buffer (50mM Tris pH 7.4, 150 mM NaCl, 2.5 mM EDTA, 2.5 mM EGTA, 0.5% NP40, 0.2%Triton X100) supplemented with “Complete” protease inhibitor cocktailfrom Roche, for 30 minutes on ice at 4° C., followed by centrifugationat 10,000 g for 30 minutes at 4° C. in order to obtain the so-called“soluble” mitochondrial fraction. The protein concentration of thecytosol and mitochondrial fractions was determined by the bicinchoninicacid (BCA) method (Bio-Rad).

B. Results

B-1. Q-VD-OPh Inhibits Activation of Caspases-3 and -8.

The effectiveness of Q-VD-OPh in inhibiting activation of caspase-3 and-8 was analyzed by immunoblot (Western blot). CD4⁺ T lymphocytes inculture were infected by the HIV-1 virus and then stimulated, 2 hoursafter infection, by Concanavalin A and IL-2. Following stimulation, 10μM of inhibitor Q-VD-OPh were added to the cell culture. Q-VD-OPh wasadded again 36 hours (3 days) and then 96 hours (4 days) afterinfection, still at a final concentration of 10 μM. Protein extractionand immunoblot were carried out on the 6th day post-infection.

The results obtained (see FIG. 1) show that, in the absence of viralinfection, caspase-3 and -8 are substantially in forms p32 and p55,respectively, which correspond to the inactive forms (proforms) ofcaspase-3 and -8. The intermediate forms p20 for caspase-3 and p44, p26and p20 for caspase-8 are also found (Alam et al., 1999; Petit et al.,2002).

When the CD4+ cells were infected by HIV-1 and then cultivated in theabsence of inhibitor Q-VD-OPh, it is found, on the 6th daypost-infection, that the proforms p32 and p55 are detected only weakly,while the intermediate forms are present in a larger amount. Moreover,the presence of forms p17 and p18, which correspond to the active forms(apoptogenic forms) of caspase-3 and -8, respectively, is detected. Thisreflects the activation of caspase-3 and -8 by proteolysis following theviral infection.

When the CD4+ cells were infected by the HIV-1 virus and cultivated inthe presence of the inhibitor Q-VD-OPh, inhibition of the proteolyticdegradation of caspase-3 and -8 is observed; the active forms p17 andp18 are not detected, while the intermediate forms and the proforms p32and p55 are detected much more strongly than when no inhibitor isadministered to the cells infected by HIV. Consequently, the use of theinhibitor Q-VD-OPh has the effect of inhibiting the proteolyticdegradation of the proforms of caspase-3 and -8 and accordingly ofblocking the activation of caspase-3 and -8.

B-2. Q-VD-OPh Inhibits Cell Death Caused by HIV-1 Infection.

The inventors evaluated the effect of the compound Q-VD-OPh on celldeath caused by HIV-1 infection and on viral replication by analyzingCD4+ T cells infected by the HIV-1 virus and then stimulated byConcanavalin A and IL-2 and incubated or not incubated in the presenceof Q-VD-OPh for 5 days (FIG. 2). Analysis of the size and granulometryof the CD4+ T cells (FIG. 2A) as well as the percentage of CD4+ cellsexhibiting mitochondrial depolarization, which is characteristic of celldeath (FIG. 2B), shows that HIV-1 infection is accompanied by apronounced increase in cell death of the CD4+ T cells (63.1% comparedwith 13.3% for the untreated cells). On the other hand, when the CD4+ Tcells were incubated with the inhibitor Q-VD-OPh after having beeninfected by HIV-1, only a slight increase in cell death of the CD4+ Tcells is observed (19.8% as compared with 13.3% for the untreatedcells). These results show that Q-VD-OPh is a potent inhibitor of celldeath resulting from HIV-1 infection, unlike other broad-spectrumcaspase inhibitors, such as zVAD-kmk, which prevents the apoptoticphenotype (condensation and fragmentation of the nuclear chromatin) incells infected by HIV but does not prevent either mitochondrialdepolarization or cell death (Petit et al., 2002).

B-3. Q-VD-OPh Inhibits Apoptogenic Mitochondrial Damage Caused by ViralReplication.

The inventors analyzed, by immunotransfer (Western blot), the effect ofQ-VD-OPh on the release of apoptogenic mitochondrial factors caused byviral replication. Primary CD4+ T cells were infected with the HIV-Laivirus and then stimulated with a concanavalin A/IL-2 cocktail beforebeing treated with Q-VD-OPh (10 μM) and/or pepstatin A (10 μM). On day 5after infection, the cells were fractionated into two parts: (i) themitochondrial membrane fraction and (ii) the cytosol fraction, which maycontain mitochondrial factors released following permeabilization of themitochondrial membrane caused by the viral infection.

Analysis of the location of the apoptogenic factors Cytochrome C,Smac/Diablo and Endonuclease G (EndoG) (FIG. 3) shows the presence ofthese apoptogenic factors in the cytosol fraction of the cells infectedby HIV-Lai, whereas in the uninfected cells they are located in themitochondrial membrane fraction, which is the indicator of mitochondrialdamage. This suggests that the massive death of the CD4+ T cellsobserved following an HIV infection is the result of a mechanism of celldeath which passes through a loss of permeability of the mitochondrialmembrane and a spreading of apoptogenic factors into the cytosol.

In addition, while the use of pepstatin A appears to have no effectafter 5 days on the mitochondrial damage caused by the viral infection,the use of Q-VD-OPh enables the presence of the apoptogenic factorsCytochrome C, Smac/Diablo and EndoG in the cytosol fraction to bereduced very considerably; the presence of Cytochrome C is even almostzero. These results show that Q-VD-OPh allows the mitochondrial damagecaused by viral replication to be reduced considerably.

B-4. Q-VD-OPh Inhibits Replication of the HIV-1 Virus.

In order to determine the effect of the compound Q-VD-OPh on viralreplication, the replication of the HIV-1 virus in the presence orabsence of Q-VD-OPh was evaluated by quantification of the number ofTCD4+ lymphocytes expressing the p24 antigen in CD4+ T lymphocytesinfected by HIV and stimulated by ConA and IL-2. Analysis of thepercentage of CD4+ T lymphocytes infected by HIV-1 on the 5th and 6thdays post-infection (FIGS. 2C and 4A, respectively) and of the amount ofthe p24 viral antigen in the culture supernatants on the 6th daypost-infection (FIG. 4B) show that the compound Q-VD-OPh reduces viralreplication by more than 75%. The inhibition of viral replication iseven stronger when the CD4+ T lymphocytes are treated both with thecompound Q-VD-OPh and with another protease inhibitor, pepstatin A(pepsin inhibitor).

FIGS. 2C and 4A show the count of cells expressing the p24 viral antigenby immunological labelling and flow cytometry. Five days afterinfection, 72.6% of the cells express the viral antigen and aretherefore infected. If the infection is followed by the addition ofQ-VD-OPh, only 18% of the cells are infected five days after infection.

B-5. The Inhibitory Effect of Q-VD-OPh on Cell Death Caused by ViralInfection and on Viral Replication is Stronger, the Earlier it isAdministered.

In order to determine if the time at which the compound O-VD-OPh isadministered has an impact on the inhibition of cell death caused byHIV-1 infection and on the inhibition of viral replication, Q-VD-OPh wasadministered to CD4+ T lymphocytes in culture either before infectionwith HIV-1 or after. In each case there was determined, by flowcytometry, on the 5th day post-infection, the percentage of CD4+ Tlymphocytes infected by the virus by intracellular labelling of the p24antigen (FIG. 7A) and the percentage of dead CD4+ lymphocytes (FIG. 7B).

The results obtained using increasing concentrations of Q-VD-OPh (0.5;1; 2; 5; 10 and 20 μM) administered to the CD4+ T lymphocytes afterinfection by HIV-1 show that the inhibition of viral replication and theinhibition of cell death caused by the viral infection aredose-dependent.

The fact that a high concentration of inhibitor (20 μM) is accompaniedby pronounced inhibition of cell death in response to the viralinfection also emphasizes the fact that the inhibitor Q-VD-OPh is notonly absolutely non-toxic for CD4+ T cells but, on the contrary,promotes survival of CD4+ T cells infected by the HIV-1 virus. Moreover,it is possible that Q-VD-OPh blocks the death of uninfected CD4+ cells(bystander effect; Hurtrel et al., 2005).

Furthermore, when Q-VD-OPh is added before infection by HIV-1 (at afinal concentration of 10 μM), inhibition of viral replication andinhibition of cell death are even greater than when Q-VD-OPh is addedbefore infection by HIV-1 (in a concentration of from 0.5 to 20 μM).This shows that the effect of the inhibitor Q-VD-OPh on the viralinfection and on the consequences of the viral infection is greater, theearlier it is administered. Accordingly, the inhibitor Q-VD-OPh may beused not only to treat a viral infection but also prophylactically, inorder to prevent a viral infection.

B-6. Q-VD-OPh Inhibits the Expression of a Group of HIV-1 Proteins inPrimary CD4+ T Cells.

The inventors analyzed the expression, on the 6th day post-infection, ofthe HIV-1 proteins in the cytosol fractions, the soluble membranefractions and the insoluble membrane fractions of CD4+ T lymphocytesinfected by the HIV-1 virus and then incubated in the presence orabsence of the compound Q-VD-OPh. The expression profile obtained (seeFIG. 6) shows that the inhibitor Q-VD-OPh drastically reduces thetotality of HIV proteins expressed in the cytosol and in the membranefractions of the primary CD4+ T lymphocytes. On the other hand, thepresence of inhibitors does not cause different compartmentalization ofthe proteins nor an accumulation of the proforms. Q-VD-OPh therefore hasan inhibitory effect for the expression of the totality of the viralgenome but has no effect on intracellular protein traffic and thereforeon the maturation of the proteins.

B-7. Q-VD-OPh Inhibits the Replication of Primary HIV-1 Strains.

Viral replication was analyzed by flow cytometry in CD4+ T lymphocytesinfected by the HIV-1 Lai virus or with the serum of a chronic HIV+patient containing a primary strain with X4/R5 dual tropism.

In the case of the HIV-1 Lai virus, as in the case of the serum of achronic HIV+ patient, it is noted that, when the lymphocytes infected bythe virus were cultivated in the presence of the compound Q-VD-OPh,viral replication is strongly inhibited (FIG. 5A). 3.79% of infectedcells treated with Q-VD-OPh, as compared with 36.46% of the cells nottreated with Q-VD-OPh in the case of an infection by the strain LAI and0.06% of infected cells treated with Q-VD-OPh in the case of aninfection by a primary strain.

Moreover, a quantitative analysis of cell death by measurement ofmitochondrial depolarization, and of viral replication by ELISA assay ofthe p24 viral antigen in CD4+ T lymphocytes infected with the serum ofthe chronic HIV+ patient show that Q-VD-OPh also causes stronginhibition of cell death (total or almost total inhibition) and of viralreplication (FIG. 5B) on a primary isolate of the HIV-1 retrovirus.

The inventors further analyzed the replication of five primary HIV-1isolates taken from HIV+ patients, of R5 tropism, in the absence orpresence of the inhibitor Q-VD-OPh or of ddl, a reverse transcriptaseinhibitor. It is noted that, for the five primary isolates, Q-VD-OPh andddl have a similar effect, namely strong inhibition of viral replication(see FIG. 5C). The viral strains with R5 tropism are those which arefound most commonly and have the characteristic of emerging early duringthe infection and of persisting throughout the evolution of the disease,whereas the viral strains with X4 tropism tend to be late strains. Theability of Q-VD-OPh to inhibit viral replication more particularly ofthe viral strains with R5 tropism renders this molecule very interestingfrom a therapeutic point of view because it may be used to stop a viralinfection at a very early stage.

B-8. Q-VD-OPh Inhibits Replication of the SIVmac251 Virus and theFormation of Syncytia.

In order to evaluate the field of application of the antiviralproperties of the inhibitor Q-VD-OPh, the inventors analyzed the effectof Q-VD-OPh on replication of the SIVmac251 virus and on the formationof syncytia (FIG. 8). The cell line CEMx174 was infected with a strongdose of virus of the strain SIVmac251 (200 AID50), which corresponds toten times the concentration used to infect monkeys. Analysis of viralproduction in the culture supernatant by RT-PCR on the 4th and 5th dayspost-infection shows that replication of the SIVmac251 virus isinhibited in the presence of the inhibitor Q-VD-OPh, in a dose-dependentmanner. Moreover, when a high concentration of inhibitor (20 μM) isadministered, viral replication is inhibited by more than 70%.Consequently, it appears that Q-VD-OPh inhibits replication of the HIVand SIV viruses in a similar manner.

In addition, the formation of syncytia, a characteristic which would belinked to greater or lesser virulence, is likewise strongly inhibitedunder the effect of the inhibitor Q-VD-OPh. However, a concentration ofQ-VD-OPh equal to or greater than 10 μM is required to obtain a 70%reduction in the number of syncytia 5 days after infection andtreatment.

These results show that Q-VD-OPh is a broad-spectrum viral replicationinhibitor which allows not only HIV viruses but also SIV viruses to beblocked.

B-9. Q-VD-OPh Acts in Synergy with AZT and Indinavir to Inhibit ViralReplication and Death of the CD4⁺ T Lymphocytes.

The inventors tested the hypothesis according to which the inhibitorQ-VD-OPh might have a synergistic effect with other antiviral moleculesused in combating HIV, in particular with azidothymidine (AZT), areverse transcriptase inhibitor, and with Indinavir, a proteaseinhibitor. Primary CD4+ T cells were infected by an HIV-Lai virus andthen stimulated with concanavalin A and IL-2. The cells were thencultivated in the presence or absence of Q-VD-OPh (0.1, 1 or 10 μM) andin the presence or absence of AZT (0.1 μM) or Indinavir (1 μM). Wherethe drugs were added to the culture, they were added 96 hours (d3) afterinfection. Cell death was then quantified by flow cytometry on the 5thday post-infection.

The results obtained (FIG. 9) show that Q-VD-OPh, when used incombination with AZT or Indinavir, inhibits cell death resulting fromviral infection much more strongly than Q-VD-OPh, AZT or Indinavir usedalone. Consequently, Q-VD-OPh used in association with anti-HIVtreatments for preventing cell death, which is a consequence of viralreplication, gives rise to a synergistic effect.

C. Conclusion

The totality of these works clearly shows that the compound Q-VD-OPh isa potent inhibitor of the replication of the HIV and SIV viruses. Themore effective inhibitory effect of Q-VD-OPh when administered beforeinfection (pretreatment—see Example B5) shows, moreover, that thismolecule acts during the first stages of the replication cycle of thevirus. The compound Q-VD-OPh is therefore of major interest fortherapeutic use as an antiviral agent and in particular as anantiretroviral agent, and as an antilentiviral agent.

Furthermore, the ability of Q-VD-OPh to prevent apoptosis may be anadditional advantage allowing the immune response in respect ofpathogenic agents to be restored in a more consistent manner.

It is to be noted that the use of another broad-spectrum caspaseinhibitor z-VAD-fmk does not inhibit apoptosis of those cells duringviral replication (Petit et al., 2002) nor does it inhibit viralreplication of HIV or the death of the T lymphocytes induced by HIVinfection (Petit et al., 2002), suggesting that this new inhibitor mayhave a major role in the fight against this viral infection.

In addition, Q-VD-OPh is capable of acting in synergy with otherantiviral molecules such as AZT and Indinavir. The use of Q-VD-OPh inassociation with other antiviral molecules, in particular with othermolecules from the range of anti-HIV agents currently available,therefore appears particularly promising.

Example 2 Comparative Analysis A. Material and Methods

Analysis by Flow Cytometry of the Fall in λφm and of the p24 Protein ofthe HIV Virus

In order to evaluate the change in the transmembrane potential of theinner mitochondrial membrane, the cells were labelled with a fluorescentprobe DIOC₆ (Molecular Probes, Invitrogen), at a concentration of 40 nM,and incubated for 15 minutes at 37° C. Viral replication was evaluatedby internal labelling of the p24 viral protein using an anti-p24-PEantibody (KC-57, Coulter Corp, Beckman).

Immunoblot

20 μg extracts of total lysate prepared with 1% NP40 were boiled for 5minutes in Laemmli buffer containing 2% SDS and 10% 2-β-mercaptoethanol,then deposited on 10-20% polyacrylamide gradient gels (Invitrogen).After transfer of the proteins, the immunoblots were incubated with thefollowing primary antibodies: anticaspase-3, anticaspase-8 andanticaspase-9 (Cell Signaling), anti-PARP (Pharmingen) and anti-Tubulin(Santa-Cruz). The secondary antibodies coupled to peroxidase(horseradish) (Amersham Biosciences) allows the proteins to be revealedby chemiluminescence (ECL, Amersham) using a CCD camera (G:Box-Chemi-XT16-SynGene).

Synthetic Inhibitors and other Chemical Products

The broad-spectrum caspase inhibitor Z-VAD-fmk (Calbiochem), the generalcaspase inhibitor: Q-VD-OPH, the caspase-8 inhibitor: Q-IETD-OPH, thecaspase-3, -7 inhibitor: Q-DEVD-OPH and the caspase-9 inhibitor:Q-LEHD-OPH (MP Biomédicals, France) were used. The anti-CD95 antibody(human Fas) (clone 7C11, Immunotech) was used to induce apoptosis. TheHIV antiproteases Saquinavir, Ritonavir and Indinavir are obtained fromNIH. The probe CFSE (carboxyfluorescein diacetate succinimidyl ester)used for the proliferation study was obtained from Molecular Probes(Invitrogen).

Proliferation Test with CFSE

The PBMCs are incubated in the presence of 1 μM of CFSE for 7 minutes at37° C. The cells are taken up at 1.10⁶/ml and then placed in culture andactivated by an anti-CD3 at 1 μg/ml (Immunotech).

B. Results

B-1. Validation of New Caspase Inhibitors

B-1-a. Determination of the Functionality of New Specific Caspase-3, -8and -9 Inhibitors in Respect of Apoptosis Induced by Fas/CD95.

Jurkat cells were incubated in the presence or absence of anti-CD95 atdifferent concentrations in order to determine a dose-response curve forapoptosis. Death was evaluated by analyzing the fall in themitochondrial transmembrane potential (% Δφm low) using the probe DIOC6,by flow cytometry (FIG. 10A). The same experiment was then conducted inthe presence of 0.25 μg/ml of anti-CD95 and different caspaseinhibitors. The apoptosis induced by anti-CD95 is expressed by thepercentage Δφm low analyzed by flow cytometry (FIG. 10B).

Jurkat cell extracts which have been treated in the presence or absenceof anti-CD95 and of the different caspase inhibitors were analyzed byimmunoblot for caspase-3, -8, -9 and PARP (substrate specific tocaspase-3 and -7), tubulin is used as control for the deposits (FIG.10C).

B-1-b. Determination of the Ability of the Specific Inhibitors toInhibit Viral Replication and Consequently Cell Death.

Primary CD4 T cells were infected by the viral strain HIV-Lai and thenstimulated by ConA/IL-2 in the presence or absence of Q-VD-OPH,Q-DEVD-OPH (casp-3 inhibitor), Q-LEDH-OPH (caspase-9 inhibitor) andQ-IETD-OPH (caspase-8 inhibitor) at 10 μM for each of the inhibitors. Ondays 5 and 7 post-infection, the internal p24 viral protein is measuredby flow cytometry after fixation and permeabilization of the CD4 Tcells. The results show a weak effect on inhibition of viral replicationfor each of the different specific caspase inhibitors on d5 and anabsence of protection at d7; Q-VD-OPH, on the other hand, inhibitsreplication completely (FIG. 11A). Death was evaluated by analysis ofthe fall in the mitochondrial transmembrane potential (% Δφm low) usingthe probe DIOC6 by flow cytometry (FIG. 11B). We show an absence ofeffect of these inhibitors, contrary to Q-VD-OPH. Extracts of primaryCD4 T cells infected in the presence or absence of the different caspaseinhibitors as well as QVD-OPH were analyzed by immunoblot for the HIVviral proteins (FIG. 12). The results show that the quantity of viralproteins produced in the presence of the different inhibitors isslightly lower than that of the control cultures, but that viralproduction is very markedly reduced in the presence of QVD-OPH. Theseresults are in agreement with our observations regarding the detectionof the p24 protein by flow cytometry.

B-2. Toxic Effects of the Drugs

B-2-a. QVD-OPH at 50 μM does not Block the Proliferation of LymphocytesStimulated by 1 μg/ml of Anti-CD-3.

A lymphocyte proliferation study was conducted with the fluorescentprobe CFSE, which allows cell division to be monitored. The PBMCs arestimulated with anti-CD3 at 1 μg/ml and incubated in the presence orabsence of the HIV antiproteases Saquinavir, Ritonavir and Indinavir, atconcentrations of 1 μM, 10 μM and 50 μM, as well as QVD-OPH at 10 μM, 50μM and 100 μM. Analysis of CFSE carried out after 4 and 5 days'stimulation shows, by flow cytometry, that the HIV antiproteases blockthe proliferation of lymphocytes at a dose of 50 μM. QVD-OPH, on theother hand, at the same concentrations, has no effect on lymphocyteproliferation (FIG. 13).

The cell toxicity was evaluated by analysis of the fall in themitochondrial transmembrane potential (% Δφm low) using the probe DIOC6,by flow cytometry. The cells stimulated by anti-CD3 were analyzed in thesame way on the day following activation. Accordingly, QVD-OPH, even athigh concentrations (100 μM), has no effect on mitochondrialdepolarization (compared with the control), whereas Indinavir andSaquinavir show a fall in Δφm of more than 70-80% at a dose of 50 μM(FIG. 14).

B-2-b. Evaluation of the Toxicity of QVD-OPH in Respect of Lymphocytesand Monocytes.

PBMCs are incubated in the presence of the different HIV antiproteasesSaquinavir, Ritonavir and Indinavir, at concentrations of 1 μM, 10 μMand 50 μM, as well as QVD-OPH at 10 μM, 50 μM and 100 μM. The celltoxicity was evaluated by analysis of the fall in the mitochondrialtransmembrane potential (% Δφm low) after 4 days' culture by analyzingthe monocytes and lymphocytes. The effect of QVD-OPH on mitochondrialdepolarization remains minimal on one or other of the populations evenat a concentration of 100 μM, while the HIV antiproteases, in particularSaquinavir, show depolarization of more than 90% (FIG. 15A and B). Theseresults are in agreement with our previous works.

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1. Compound of structure I: A-B-C, in which: A is a quinoline orquinoline-type group, B is a single amino acid or a peptide orpolypeptide having a given amino acid sequence, C is an O-phenoxy group,and the symbol “-” indicates that the entities A, B and C are chemicallybonded within the compound I, for use in the prophylaxis and/ortreatment of a viral infection.
 2. Compound according to claim 1, inwhich the structure I is:

in which: B is a single amino acid or a peptide or polypeptide having agiven amino acid sequence, R1 and R2 are selected from a hydrogen, analkyl, an alkoxy, a fluoro, a chloro, a carboxy, a carbonyl, anarylcarbonyl and an amino, and R3 and R4 are selected from a hydrogen,an alkyl, an alkoxy, a fluoro, a chloro, a carboxy, a carbonyl, anarylcarbonyl and an amino.
 3. Compound according to claim 1, in which Bis a peptide or polypeptide, in particular a peptide having a di-, tri-or tetra-peptide sequence.
 4. Compound according to claim 1, in whichthe single amino acid is an aspartic acid (D) or said peptide orpolypeptide comprises at least one aspartic acid.
 5. Compound accordingto claim 1, in which said peptide or polypeptide comprises an asparticacid (D) and a valine (V).
 6. Compound according to claim 1, in whichthe amino acid sequence of said peptide is the sequence Valine-Asparticacid (VD) or the sequence Valine-Alanine-Aspartic acid (VAD). 7.Compound according to claim 1, in which the single amino acid or atleast one of the amino acids of said peptide or polypeptide isO-methylated.
 8. Compound according to claim 1, in which said compoundis O-methylated on the single aspartic acid or on at least one of theaspartic acids of said peptide or polypeptide.
 9. Compound according toclaim 1, in which the single amino acid or the amino acid sequence ofsaid peptide or polypeptide is not O-methylated.
 10. Compound accordingto claim 2, in which R1 and/or R2 is a hydrogen.
 11. Compound accordingto claim 2, in which R3 and/or R4 is a fluoro.
 12. Compound according toclaim 1, in which the compound of structure I is a protease inhibitor,in particular a caspase inhibitor.
 13. Compound according to claim 1,for use in inhibiting: at least one caspase selected from theinflammatory caspases (group I), in particular caspase-1, -4, -5, -11,-12, -13 and -14, more particularly caspase-1 and -12; and/or at leastone caspase selected from the initiator caspases (group II), inparticular caspase-2, -8, -9 and -10, more particularly caspase-8 and-10; and/or at least one caspase selected from the effector caspases(group III), in particular caspase-3, -6 and -7, more particularlycaspase-3.
 14. Compound according to claim 1, in which said compound ofstructure I is the compound Q-VD-OPh, of structureN-(2(quinoly)valyl-O-methyl-aspartyl-(2,6-difluorophenoxy)methyl ketoneor N-(2(quinolyl)valyl-aspartyl-(2,6-difluorophenoxy)methyl ketone. 15.Compound according to claim 1, in which said viral infection is causedby a DNA virus or an RNA virus.
 16. Compound according to claim 15, inwhich said virus is a virus selected from the following families: theflaviviridae, in particular the genus flavivirus, for example the dengueviruses and the yellow fever virus; the orthomyxoviruses, represented bythe influenza viruses; the paramyxoviridae, in particular the genusmorbillivirus, especially the measles virus, and the genus pneumovirus,for example human respiratory syncytial virus and metapneumovirus; thereoviridae, in particular the genus rotavirus; the picornaviridae, inparticular the genus enterovirus, represented by the polioviruses andthe viruses responsible for viral meningitis, the genus aphthovirus,especially the aphthous fever virus, and the genus rhinovirus; thefiloviridae, in particular the Ebola virus; the arenaviridae, inparticular the Lassa virus; the rhabdoviridae, in particular the genusrhabdovirus, including the rabies viruses, and the genus vesiculovirus,which includes the vesicular stomatitis virus; the togaviridae, inparticular the genus Rubivirus, including the rubella virus; thepoxviridae, in particular the vaccinia and variola viruses; theherpesviridae, in particular the Herpes, varicella and Zona viruses; thehepatitis A, B, C, D and E viruses; the coronaviridae, in particular thegenus coronavirus, for example the SARS virus; the retroviruses, inparticular the genus lentivirus and the genus oncovirus, for example theHTLV-1 virus.
 17. Compound according to claim 15, in which said virus isa human retrovirus, in particular a human lentivirus.
 18. Compoundaccording to claim 17, in which said human retrovirus is a humanimmunodeficiency virus (HIV), in particular HIV-1 or HIV-2.
 19. Compoundaccording to claim 17, in which said human retrovirus is HIV-1. 20.Compound according to claim 15, in which said virus is a simianretrovirus, in particular a simian lentivirus.
 21. Compound according toclaim 20, in which said simian retrovirus is a simian immunodeficiencyvirus (SIV).
 22. Compound according to claim 1, in which said viralinfection is selected from the group constituted by viral encephalitis,viral meningitis, aphthous fever, influenza, yellow fever, respiratoryvirus infections, infantile diarrhoea, heamorrhagic fevers,poliomyelitis, rabies, measles, rubella, varicella, smallpox, herpeszoster, genital herpes, hepatitises A, B, C, D and E, SARS, leukaemiaand paralysis due to HTLV-1, and infections caused by an HIV virus, inparticular acquired immunodeficiency syndrome (AIDS).
 23. Compoundaccording to claim 15 for use in preventing and/or inhibiting viralreplication in an animal or human infected by said virus.
 24. Compoundaccording to claim 15 for use in preventing and/or inhibiting viralprotein synthesis in an animal or human infected by said virus. 25.Compound according to claim 1, in which said viral infection correlateswith an increase in cell death in an animal, in particular with anincrease in the death of the T cells, and more particularly with anincrease in the death of the CD4+ T cells, in a human infected by saidvirus.
 26. Compound according to claim 15 for use in, further,preventing and/or inhibiting an increase in cell death in an animalinfected by said virus.
 27. Compound according to claim 26 for use inpreventing and/or inhibiting an increase in the death of the Tlymphocytes, in particular an increase in the death of the CD4⁺ Tlymphocytes.
 28. Compound according to claim 23, in which said animal isa non-human mammal, in particular an ape or a cat.
 29. Compositioncomprising as active ingredient the compound according to claim 1 andfurther comprising one or more carrier(s), diluent(s) or adjuvant(s) ora combination thereof, for use in the prophylaxis and/or treatment of aviral infection.
 30. Composition according to claim 29, characterized inthat it is formulated for administration by the enteral, parenteral(intravenous, intramuscular or subcutaneous), transcutaneous, cutaneous,oral, mucosal, in particular transmucous-buccal, nasal,ophthalmological, otological, vaginal or rectal route, or alternativelyby the intragastric, intracardiac, intraperitoneal, intrapulmonary orintratracheal routes.
 31. Compound according to claim 1, characterizedin that it is administered to an animal or human before said animal orhuman is exposed to said virus and/or during exposure to the virusand/or after exposure to the virus, in particular within 48 hours ofsaid animal or human being exposed to said virus.
 32. Compound accordingto claim 1, characterized in that said compound or composition isadministered several times in succession.
 33. Antiviral compositioncomprising or consisting of: (i) at least one compound of structure I asdefined in claim 1; and (ii) at least one other antiviral agent, inparticular at least one other antiretroviral agent.
 34. Antiviralcomposition according to claim 33, further comprising one or morecarrier(s), diluent(s) or adjuvant(s) or a combination thereof.
 35. Acombination comprising or consisting of: (i) at least one compound ofstructure I as defined in claim 1; and (ii) at least one other antiviralagent, in particular at least one other antiretroviral agent, in whichcompounds (i) and (ii) are separate from one another.
 36. Combinationaccording to claim 35, in which compounds (i) and (ii) are present intwo distinct compositions.
 37. Combination according to claim 35, inwhich compounds (i) and (ii) are formulated for simultaneousadministration in terms of time.
 38. Combination according to claim 35,in which said compound(s) (i) is(are) formulated for sequentialadministration preceding and/or following administration of saidcompound(s) (ii).
 39. Combination according to claim 36, in which thecomposition comprising compound (i) and/or the composition comprisingcompound (ii) further comprises one or more carrier(s), diluent(s) oradjuvant(s) or a combination thereof.
 40. Antiviral compositionaccording to claim 33 or combination, in which said other antiviralagent is selected from: transcriptase inhibitors; viral proteaseinhibitors (or antiproteases); inhibitors of the fusion of the viralenvelope with the cell membrane; receptor or coreceptor inhibitors;antisense oligonucleotides; integrase inhibitors; and molecules thattarget other steps of viral multiplication.
 41. Antiviral composition orcombination according to claim 33, in which said other antiviral agentor at least one of said other antiviral agents consist(s) of at leastone transcriptase inhibitor and/or at least one viral proteaseinhibitor.
 42. Antiviral composition or combination according to claim40, characterized in that the transcriptase inhibitor is a reversetranscriptase inhibitor, in particular an HIV virus reversetranscriptase inhibitor.
 43. Antiviral composition or combinationaccording to claim 40, characterized in that the reverse transcriptaseinhibitor is selected from the group constituted by zidovudine orazidothymidine (AZT), didanosine or ddl, zalcitabine or ddC, stavudineor d4T, lamivudine or 3TC, abacavir or ABC, and emtricitabine or FTC,nevirapine, efavirenz, delavirdine and tenofovir or bis-POC-PMPA. 44.Antiviral composition or combination according to claim 40,characterized in that the reverse transcriptase inhibitor is AZT. 45.Antiviral composition or combination according to claim 40,characterized in that the viral protease inhibitor is an HIV virusprotease inhibitor.
 46. Antiviral composition or combination accordingto claim 40, characterized in that the viral protease inhibitor isselected from the group constituted by Indinavir or IDV, Nelfinavir orNLFN, Saquinavir or SQN, Ritonavir or RTN, Amprenavir and Lopinavir. 47.Antiviral composition or combination according to claim 40,characterized in that the viral protease inhibitor is Indinavir. 48.Antiviral composition or combination according to claim 33, in whichsaid compound(s) (i) act(s) in synergy with said compound(s) (ii). 49.Antiviral composition or combination according to claim 33, in whichcompounds (i) and (ii) are formulated for administration by the enteral,parenteral (intravenous, intramuscular or subcutaneous), transcutaneous,cutaneous, oral, mucosal, in particular buccal, nasal, oesophageal,vaginal or rectal route, or alternatively by the intragastric,intracardiac, intraperitoneal, intrapulmonary or intratracheal routes.50. Antiviral composition or combination according to claim 33 for useas a medicament, in particular as an antiviral agent, and moreparticularly as an antiretroviral agent.
 51. Antiviral composition orcombination according to claim 33 for use in the prophylaxis and/ortreatment of a viral infection, in particular for preventing and/orinhibiting viral replication, in an animal or human.
 52. Antiviralcomposition or combination according to claim 50 for use, further, forpreventing and/or inhibiting an increase in cell death, in particular anincrease in the death of the T lymphocytes, and more particularly anincrease in the death of the CD4⁺ T lymphocytes, in an animal or humaninfected by a virus.
 53. Antiviral composition or combination accordingto claim 51, in which said animal is a non-human mammal, in particularan ape or a cat.
 54. Antiviral composition or combination according toclaim 51, in which said virus is a virus selected from the followingfamilies: the flaviviridae, in particular the genus flavivirus, forexample the dengue viruses and the yellow fever virus; theorthomyxoviruses, represented by the influenza viruses; theparamyxoviridae, in particular the genus morbillivirus, especially themeasles virus, and the genus pneumovirus, for example human respiratorysyncytial virus and metapneumovirus; the reoviridae, in particular thegenus rotavirus; the picornaviridae, in particular the genusenterovirus, represented by the polioviruses and the viruses responsiblefor viral meningitis, the genus aphthovirus, especially the aphthousfever virus, and the genus rhinovirus; the filoviridae, in particularthe Ebola virus; the arenaviridae, in particular the Lassa virus; therhabdoviridae, in particular the genus rhabdovirus, including the rabiesviruses, and the genus vesiculovirus, which includes the vesicularstomatitis virus; the togaviridae, in particular the genus Rubivirus,including the rubella virus; the poxviridae, in particular the vacciniaand variola viruses; the herpesviridae, in particular the Herpes,varicella and Zona viruses; the hepatitis A, B, C, D and E viruses; thecoronaviridae, in particular the genus coronavirus, for example the SARSvirus; the retroviruses, in particular the genus lentivirus and thegenus oncovirus, for example the HTLV-1 virus.
 55. Antiviral compositionor combination according to claim 51, in which said viral infection isselected from the group constituted by viral encephalitis, viralmeningitis, aphthous fever, influenza, yellow fever, respiratory virusinfections, infantile diarrhoea, heamorrhagic fevers, poliomyelitis,rabies, measles, rubella, varicella, smallpox, herpes zoster, genitalherpes, hepatitises A, B, C, D and E, SARS, leukaemia and paralysis dueto HTLV-1, and infections caused by an HIV virus, in particular acquiredimmunodeficiency syndrome (AIDS).